Software Support International was one of the major mail order companies for Commodore 64 software and hardware. They sold stuff for other computers of the time also but I mostly remember their ads from various Commodore 64 related magazines in the late 80s. I believe I bought Pool of Radiance from them when it came out in 1988.
This ad is from 1994 and probably came pretty late in the life of Software Support International, or at least the Commodore side of their business. Commodore had just gone out of business and the last major Commodore 64 magazine had stopped publication in 1992. No major new Commodore 64 titles were being produced at this point so the vast majority of what they were selling had to have been old stock. Their earlier ads usually had large lists of software titles and hardware items in small print so it's pretty obvious their supply was much reduced. I can't imagine that they were in business long after this, at least not selling Commodore 64 related items.
Check out some of my other recent retrogaming and retrocomputing posts!
MacAddict (June 1999)
GamesMaster (January 1993)
Nintendo Power (December 1991)
The One (July 1990)
Tips & Tricks (January 1996)