Question: Which store served by Connoisseur's Bakery is actually a symbol group of independent retailers? 

Context paragraphs:
Honigsberger Store: The Honigsberger Store is a historic building located at 665 Main St. in Copperopolis, California.  Businessman L. Honigsberger built the store in 1865, replacing the original store he built in 1861.  The brick building was designed in the Neoclassical style.  The store served Copperopolis during its first copper boom in the 1860s; however, an 1867 fire and declining copper production caused Copperopolis to lose most of its population and severely diminished the store's business.  In 1905, the Honigsberger family sold the store to the Union Copper Mining Company, which became the Calaveras Copper Mining Company four years later.  The company used the store as a warehouse during another copper boom in Copperopolis from 1909 to 1929.  The store is one of only four extant buildings from Copperopolis' first copper boom in the 1860s.

Nisa (retailer): Nisa Retail Limited (formerly Nisa-Today's) is a brand and buying group (or "symbol group") of independent retailers (primarily small grocery shops) and wholesalers in the United Kingdom.  It is a mutual organisation owned by its members and operating "...like a co-operative, using the collective buying power of the large group of members to negotiate deals with suppliers".

Musgrave Retailer Services: Musgrave Retailer Services supplies the "Day Today" and "Day Break" symbol group of convenience retailers, the principal forecourt operators and other independent retailers throughout Ireland.  In all, the division services 32,000 regular retail and catering trade customers, accounting for an estimated 33 per cent of the Irish wholesale market.

Mica DIY: Mica is the brand name of the voluntary trading group "Mica DIY Ltd" (also referred to as a Symbol group) for independent do it yourself (DIY) and hardware retailers in the UK, who work together for group benefit in marketing, buying and retail support.

Luther Store: The Luther Store is a historic store at 160 Old Warren Road in Swansea, Massachusetts.  It is a 2-1/2 story brick structure with a saltbox profile.  Its main facade is five bays wide, with entrances in the second and fourth bays, and interior chimneys at each end.  The store retains original fixtures, including solid mahogany counters, drawers for goods storage, and the proprietor's desk.  The store was built in 1815 by John Brown Luther, and was operated by the Luther family as a store until 1903.  The Luther's Corner area was in the mid-19th century the economic center of Swansea, and Luther's Store served as post office and library.  It was acquired in 1941 by the Swansea Historical Society, which now operates it as a local history museum.

Kamp Store: The Kamp Store is a historic general store building located at the northeast corner of Oak and Broadway in Kampsville, Illinois, United States.  Joseph Kamp, the son of the founder of Kampsville, opened the store in 1902.  The two-story wood frame building features a false front with decorative metalwork.  The store provided Kampsville residents with a wide variety of goods, ranging from small household items to automobiles and heavy farming equipment.  St. Louis-based suppliers shipped the store its goods via Mississippi River barges.  Kamp operated the store until his death in 1952; the store served as a grocery store until the 1970s and later became a carpet store.  The Center for American Archeology purchased the building in 1991 and now uses it as its Visitor's Center and Museum.

Proton (supermarkets): Proton is a Greek based retail chain of independent retailers (primarily grocery shops) operating as a brand and buying group (or symbol group).  All stores are independently owned.  The parent company (ELETA LTD) is communally owned with each retailer owning a share.  As of 2006, the Proton retail network consists of around 390 stores throughout Greece.  They also sell their own brand of cola, Proton Cola.

Symbol group: Symbol group is a mainly British term for a form of franchise in the retail sector.  They do not own or operate stores, but act as suppliers to independent grocers and small supermarkets and produce stores which then trade under a common banner.  Unlike other forms of franchise, they have expanded primarily by selling their services to existing stores, rather than by actively developing new outlets.  SPAR is a well known symbol group with stores in many countries.  There are several smaller symbol groups in the United Kingdom, such as Londis, Costcutter, Premier Stores and Nisa.

Connoisseur's Bakery: Connoisseur's Bakery (commonly referred to simply as Connoisseurs) is a large bakery company in Newtownards, Northern Ireland.  It serves cities, towns and villages in County Down and County Antrim.  It serves many stores across these counties including The Griffin (until its closure in 2012), Spar, Centra, Vivo, Costcutter, Nisa and Mace.

Houston Coal Company Store: The Houston Coal Company Store, also known as the Koppers Store, is an intact example of a coal company store, located at Carswell, West Virginia.  The 1923 Italian Renaissance building possesses a detailed brick exterior and a clay tile roof, with skylights at the roof's peak.  The store served a small mining community of Carswell, West Virginia, first for the Houston Coal Company and later for the Koppers Coal Company.  Another store, now disappeared, served the upper end of the long hollow.  The store is surrounded by an expansive lawn, bordered by a stream.

Supporting paragraphs: Connoisseur's Bakery Nisa (retailer)
Answer: Nisa