<PAGE>

                                                                   EXHIBIT 10(e)

                                                    No. 2521-0027-E001

                                   ENDORSEMENT

Attached to and forming part of the CASUALTY EXCESS OF LOSS REINSURANCE
AGREEMENT No. 2521-0027 between MERCHANTS MUTUAL INSURANCE COMPANY, Buffalo, New
York and MERCHANTS INSURANCE COMPANY OF NEW HAMPSHIRE, INC., Concord, New
Hampshire (hereinafter collectively referred to as "Company") and AMERICAN
RE-INSURANCE COMPANY, a Delaware Corporation with Administrative Offices in
Princeton, New Jersey (hereinafter referred to as the "Reinsurer").

It is mutually understood and agreed by the parties hereto that effective
January 1, 2003, as respects the Company's in-force, new and renewal policies,
as respects losses occurring on or after said date, this Agreement is amended to
read as follows:

I.       Exclusion B., 22., is added to ARTICLE III, EXCLUSIONS, and the
         exclusion reads as follows:

         22.      All loss, cost or expense directly or indirectly arising out
                  of, resulting as a consequence of, or related to the
                  manufacture, testing, remediation, removal, disposal, use of
                  or exposure to the following, whether or not there is another
                  cause of loss which may have contributed concurrently or in
                  any sequence to a loss.

                  a.       Asbestos or materials or products containing
                           asbestos, except for the Company's Personal Lines
                           policies;

                  b.       2.4,5 Trichloroacetic acid ("2,4,5-1") or 2.3,7,8 -
                           TCDD;

                  c.       Diethylstilbestrol ("DES") in any dosage or form;

                  d.       Any intrauterine device ("IUD");

                  e.       Any product containing silicone, which is in any form
                           injected or implanted into the body;

                  f.       Phen-fen;

                  g.       Dioxin;

                  h.       Polychlorinated biphenyls;

                  i.       Lead Paint;

                  j.       Manufacture of Latex gloves;

                  k.       Manufacture of Polybutylene piping
                           (acrylonitrile-butadiene-styrene); or

                  l.       Bio-engineered products, including any food products
                           or therapeutic or diagnostic pharmaceutical products
                           which are developed using some form of
                           bioengineering.

Revised:  September 29, 2003

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                                                     No. 2521-0027-E001

II.      Contractor's Protective Liability (OCP) policy limits are added to
         ARTICLE IV, COMPANY POLICY LIMITS, and the Article reads as follows:

                                   ARTICLE IV

         COMPANY  POLICY LIMITS

         For the purpose of determining the Company Retention and the
         Reinsurer's limit of liability with respect to each Exhibit of this
         Agreement, the limits of liability of the Company with respect to any
         one Policy shall be deemed not to exceed:

<TABLE>
<S>                                                                      <C>
        Automobile Bodily Injury Liability                               $1,000,000  each person $1,000,000
                                                                         each occurrence

        Automobile Property Damage Liability                             $1,000,000 each occurrence

        Automobile Liability Combined Single Limit                       $1,000,000 each occurrence

        Uninsured/Underinsured Motorists Coverage                        $1,000,000 each person
                                                                         $1,000,000 each occurrence

        Personal Injury Protection Coverage                              $1,000,000 each occurrence

        Other Bodily Injury Liability                                    $2,000,000 each occurrence

        Other Property Damage Liability                                  $2,000,000 each occurrence

        Other Liability Combined Single Limit                            $2,000,000 each occurrence

        Section II Liability under Commercial Multiple Peril             $2,000,000 each occurrence

        Section II Liability under Businessowners                        $1,000,000 each occurrence

        Section II Liability under Homeowners Multiple Peril             $1,000,000 each occurrence

        Section II Liability under Farmowners Multiple Peril             $1,000,000 each occurrence

        Employers' Liability

        (1) In all states with Statutory Limits                          Statutory Limits
        (2) In All Other States
            (i)   Bodily Injury by Accident                              $1,000,000 each accident
            (ii)  Bodily Injury by Disease                               $1,000,000 policy limit
            (iii) Bodily Injury by Disease                               $1,000,000 each employee

        Owners and Contractors Protective Liability (OCP)                $5,000,000 each occurrence*

                                                                         *The Company warrants that it
                                                                         shall purchase facultative
                                                                         reinsurance for policies greater
                                                                         than $2,000,000 with policy limits
                                                                         not to exceed $5,000,000.
</TABLE>

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                                                     No. 2521-0027-E001

III.     Paragraph H., Terrorist Activity, of ARTICLE V, DEFINITIONS, is amended
         to add the definition of "chemical" and the definition reads as
         follows:

         The term "chemical" as used herein shall mean any substance obtained by
         a chemical process or used for producing a chemical effect for the
         purposes of Terrorist Activity.

IV.      Paragraph B. of Section 3, RETENTION AND LIMIT, of EXHIBIT A, FIRST
         CASUALTY EXCESS OF LOSS REINSURANCE COVER, is amended to reflect the
         addition of an annual aggregate limit for "NBCR" Terrorist Activity and
         the Paragraph reads as follows:

         B.       Notwithstanding the aforementioned, the following limits shall
                  apply as respects all loss, cost or expense arising from or
                  related to, either directly or indirectly, any Terrorist
                  Activity", as defined in the DEFINITIONS Article:

                           $1,250,000 Ultimate Net Loss each Occurrence and
                           $2,500,000 Ultimate Net Loss in the aggregate as
                           respects all such Occurrences for each Agreement
                           Year. However, the Reinsurer's liability shall be
                           limited to $1,250,000 in the aggregate as respects
                           all such Occurrences arising from loss as defined in
                           Paragraph H.,3.,c, of the DEFINITIONS Article for
                           each Agreement Year.

V.       Section 4, REINSURANCE PREMIUM, of EXHIBIT A, FIRST CASUALTY EXCESS OF
         LOSS REINSURANCE COVER, is amended to reflect the change in rate for
         Commercial Automobile Liability (including PIP) to x.xx%, the change in
         rate for Workers' Compensation and Employers' Liability to x.xx% and
         the change in rate for Commercial Multiple Peril (Section II), Business
         Owners (Section II), General Liability and the Liability Section of
         Contractors Coverall to x.xx%, and the Section reads in its entirety as
         follows:

                                    Section 4

         REINSURANCE PREMIUM

         A.       With respect to business in force at the effective time and
                  date of this Exhibit, the Company shall pay to the Reinsurer a
                  reinsurance premium equal to the product of the applicable
                  gross rate set forth in the Schedule of Rates below times the
                  Company's unearned premium for each class of Casualty business
                  reinsured hereunder, calculated on the monthly pro rata basis
                  as of the effective time and date of this Exhibit.

         B.       With respect to business becoming effective at and after the
                  effective time and date of this Agreement, the Company shall
                  pay to the Reinsurer a

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                                                     No. 2521-0027-E001

                  reinsurance premium equal to the product of the applicable
                  gross rate set forth in the Schedule of Rates below times the
                  Company's Gross Net Written Premium for each class of Casualty
                  business covered under this Exhibit.

                               SCHEDULE OF RATES

<TABLE>
<CAPTION>
                                       Class of Business                                     Gross Rate
                                                                                             ----------
<S>                                                                                          <C>
                  Private Passenger Automobile Liability (including PIP)                       x.xx%

                  Commercial Automobile Liability (including PIP)                              x.xx%

                  Workers' Compensation and Employers' Liability                               x.xx%

                  Commercial Multiple Peril (Section II), Business Owners (Section II),        x.xx%
                  General Liability and the Liability Section of Contractors Coverall

                  Homeowners Multiple Peril (Section II) and Farmowners Multiple Peril        No Charge
                  (Section II)
</TABLE>

VI.      Paragraph B. of Section 3, RETENTION AND LIMIT, of EXHIBIT B, SECOND
         CASUALTY EXCESS OF LOSS REINSURANCE COVER, is amended to reflect the
         addition of an annual aggregate limit for "NBCR" Terrorist Activity and
         the Paragraph reads as follows:

         B.       Notwithstanding the aforementioned, the following limits shall
                  apply as respects all loss, cost or expense arising from or
                  related to, either directly or indirectly, any Terrorist
                  Activity, as defined in the DEFINITIONS Article:

                  $3,000,000 Ultimate Net Loss each Occurrence and $6,000,000
                  Ultimate Net Loss in the aggregate as respects all such
                  Occurrences for each Agreement Year. However, the Reinsurer's
                  liability shall be limited to $3,000,000 in the aggregate as
                  respects all such Occurrences arising from loss as defined in
                  Paragraph H.,3.,c, of the DEFINITIONS Article, for each
                  Agreement Year.

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                                                     No. 2521-0027-E001

VII.     Section 4, REINSURANCE PREMIUM, of EXHIBIT B, SECOND CASUALTY EXCESS OF
         LOSS REINSURANCE COVER, is amended to reflect the change in rate to
         x.xx%, the change in the minimum premium amount to $xxx,000, the change
         in the deposit premium amount to $xxx,000, and the Section reads in its
         entirety as follows:

                                    Section 4

         REINSURANCE PREMIUM

         A.       With respect to business in force and business becoming
                  effective at and after at the effective time and date of this
                  Exhibit, the Company shall pay to the Reinsurer a reinsurance
                  premium equal to x.xx% times the Company's unearned premium
                  for the Casualty business reinsured hereunder, calculated on
                  the monthly pro rata basis as of the effective time and date
                  of this Exhibit.

         B.       The annual minimum premium for the reinsurance provided for
                  each Agreement Year hereunder is $xxx,000.

         C.       The annual deposit premium for the reinsurance provided for
                  each Agreement Year hereunder is $xxx,000.

VIII.    Section 4, REINSURANCE PREMIUM, of EXHIBIT C, THIRD CASUALTY EXCESS OF
         LOSS REINSURANCE COVER, is amended to reflect the change in rate to
         x.xx%, the change in the minimum premium amount to $xxx,000, the change
         in the deposit premium amount to $xxx,000, and the Section reads in its
         entirety as follows:

                                    Section 4

         REINSURANCE PREMIUM

         A.       With respect to business in force and business becoming
                  effective at and after at the effective time and date of this
                  Exhibit, the Company shall pay to the Reinsurer a reinsurance
                  premium equal to x.xx% times the Company's unearned premium
                  for the Casualty business reinsured hereunder, calculated on
                  the monthly pro rata basis as of the effective time and date
                  of this Exhibit.

         B.       The annual minimum premium for the reinsurance provided for
                  each Agreement Year hereunder is $xxx,000.

         C.       The annual deposit premium for the reinsurance provided for
                  each Agreement Year hereunder is $xxx,000.

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                                                     No. 2521-0027-E001

IX.      Section 5, REINSURANCE PREMIUM, of EXHIBIT D, WORKERS' COMPENSATION
         EXCESS OF LOSS REINSURANCE COVER, is amended to reflect the change in
         the minimum premium amount to $xx,000, the change in the deposit
         premium amount to $xx,000, and the Section reads in its entirety as
         follows:

                                    Section 5

         REINSURANCE PREMIUM

         A.       With respect to business in force and business becoming
                  effective at and after at the effective time and date of this
                  Exhibit, the Company shall pay to the Reinsurer a reinsurance
                  premium equal to x.xx% times the Company's unearned premium
                  for the Casualty business reinsured hereunder, calculated on
                  the monthly pro rata basis as of the effective time and date
                  of this Exhibit.

         B.       The annual minimum premium for the reinsurance provided for
                  each Agreement Year hereunder is $xx,000.

         C.       The annual deposit premium for the reinsurance provided for
                  each Agreement Year hereunder is $xx,000.

IN WITNESS WHEREOF the parties hereto have caused this Endorsement to be
executed in    this day of   , 2003;

ACCEPTED:
MERCHANTS MUTUAL INSURANCE COMPANY
MERCHANTS INSURANCE COMPANY OF NEW HAMPSHIRE, INC.

---------------------------------
and in Princeton, New Jersey this         day of                   , 2003.

                                                AMERICAN RE-INSURANCE COMPANY

                                                -----------------------
                                                Vice President

DATED: July 31, 2003

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