According to Tradingcarddatabase.com:

"Set was released by TCMA and available exclusively via mail order; advertisement was done through hobby media. The cards have a 1975 copyright but are considered a 1976 set as it was not released until then. SSPC was not licensed by either MLB Properties or the MLBPA, and shortly after its release, was sued by Topps. As part of the settlement, SSPC agreed to never reprint their 1976 set, and to never attempt to produce a similar product ever again. Keith Olbermann, then still in high school, edited the copy on each card."