Hello.

From your pictures it looks like there is not a set of water bottle holes on the seat tube and by 1991 virtually every bike was built to carry 2 water bottles. Could your bike be earlier than 1991? On the side of the top tube near the headset there is a decal - does it indicate the model for the bike? Not to question your description, but could you confirm there is 8 speeds at the back instead of 7. Have you ever replaced the cassettte/freewheel?

Let me know when you have a chance.

Ron