Actualy there are still quite a few scattered about the metro Boston area.
It's not a chain perse, but individually owned and operated.
When founded I belive it was a group of family and freinds that did this to increase their buying power. Their sandwichies were very consistant from location to location, but some of the shops offered other items not found thruout the group. I quess you could say it was somewhat the precursor of the modern day franchise system.
The locations that I know of is Sub Villa in Saugus, Santoro's of Lowell and locations in Wakefield, Malden, Peabody, Medford, Everett. I'm sure there are others but how much longer they can survive is anyones guess.