Printed finding aids are available for consultation onsite. Item level catalogues exist for these accessions and are available for consultation onsite. It is uncatalogued and difficult to work with. I have been through most of it and and have compiled a list of CN loco dwgs. and general notes on other contents. Finding uncopied originals is the difficult and time-consuming part.
Copied drawings have NMC copy negative numbers.
Online searching via ArchiviaNet ArchiviaNet provides a number of gateways to groups of records and collections. Of principle interest to railway researchers, are Records created by departments and agencies of the Federal Government and Photographic holdings . A pull-down menu of record groups is provided. ArchiviaNet has some unfortunate limitations. Those represented only by a PA number do not appear as results for keyword searches, but only when the PA number is used as a search term - a useless redundancy.