M. A. & C. RY.
On September 19 last year a cancel by the same railway appeared on this site. Since that time I have failed to identify the MA&C Railway, which is odd, since with the vast resources now available online regarding railroads the process of identification is usually short and simple. Again, if anybody might know the full name of the railroad behind these initials, please let me know at email@example.com.
Meanwhile, the best online resource I've ever found for researching railroads is Railroadiana. A screen shot of the names database search page is included below. The site is maintained by collectors and experts of railroad collectables, and they maintain a search engine in which one can search by railroad initials. This has been quite useful for me, though the Railroadiana database still produces a blank for the MA&C. Since the search engine did not help, I also posted the stamps with the MA&C initials on the question page of the Railroadiana site to see if any of those that follow the site could help provide an answer. Nobody could. So I am still stuck!
Screen capture of Railroadiana railroad names database.