Looks like a Collegiate. Known as a Camelback due to the curved top tube. Most Collegiates were 5 speeds as this one appears to be. There were also some Collegiate Sports that were ten and came with a Shimano FFS crankset. Forget the Shimano name for it but the rear cogs were semi fixed and the crankset did the freewheeling. Most Camelbacks (geared ones anyway), were based on small frames like a 48 I believe. You are correct in thinking Speedster which shared a similar design as did the Typhoon and the Corvette if memory serves. They seem to be gaining some interest of late but don’t seem to be collectible or terribly hard to find if you hunt a bit. There was also a Varsity version also a 10 speed arrangement. The Camelback Varsity, or a Camelback Collegiate Sport In 10 speed can be a elusive to find piece seemingly. I recently Resto-Modded one of each. Keep in mind they are small frames, the 10 speeds came with 27” wheels so 700s are doable fairly easily. Looong seat posts are easy to find as well in the oddball Schwinn 20.7 or 13/16” diameter.