Here are a few contributions along with my interpretations of the SNs:
1985 Univega Alpina Pro
M 552099 Univega used a lot of Miyata frames, and this SN would be consistent with Miyata's numbering system and the frame being made in 1984.
1986 Specialized Stumpjumper Sport
CS 625323 This lines up with the scheme for the mysterious Japanese factory S (1) and a March 1986 build. I bought the bike from its original owner, who had worked in a shop and ridden for a sponsored team. She had a 1985 bike, but she broke the frame in a race, and Specialized sent her a new one. Bike was pretty rough and I had the frame powdercoated; I'm not sure the Suntour roller-cam brake is salvageable.
1992 Bridgestone BB-1
M 1 I (definitely the letter i) 5808 This doesn't fit either of the Bridgestone entries in T-Mar's list, but BB stood for 'Bridgestone Basic' according to Grant Peterson’s catalog text, and it may have had humbler origins than the rest of the line. The SN is consistent with Merida and a Sept 1991 build, which fits the 1992 model year. The frame has a Made in Taiwan sticker.