Good comment but the tube goes all the way through, as you & others comment its seems on the wrong side as you say "someone who hadn't had their coffee yet" there again per a previous comment the serial number tends to indicate # 10 so maybe they were still on a learning carve !

Yes The FD cable ran underneath BB with little screw in plastic guide, & was bottom pull, I cannot believe someone would have added the tube later, it looks like part of the original manufacture.

There is a complete miss match of the few components on the bike so there is no clue there.

Assuming the seatpost is original its stamped 93-3 but I would have thought the rear drop spacing been wider by then as its only 128.mm