If the bike still has the original components on it you can check for the Shimano codes.

Yes the bike was a Marlboro promotional item, as odd as it seems.

I bought mine used about 10 years ago and it was all original with the Shimano 15 speed drive train and the heavy steel components. The frame itself is all thats left of the original bike and for a folder it does a good job. It now sports a modern Deore drive train and narrow 26" wheels. It has worked fabulously for both commuting on trains where a non folding bike was not allowed and on vacations when traveling by car and space is limited. The first picture shows it folded in the trunk of a Camry with a 62cm Fuji S-10-S below it. While the road bike had to be completely dismantled to fit, the folder just goes right in.