Thanks to all.
Sorry if I wasn't able to replay before but there is a 5 post limit in 24 hours that limits my possibility to replay immediately. I hope it is a limit that is only temporary for newer user. Isn't it?
Anyway the bike has Shimano transmission components with a BD date code so it should be of April 1993.
At that time I was 17 and I had already reached my actual height.
Moreover the same bike was sold to my brother who was (and still is) 10 cms higher than me.
My height at the crotch is 83 cm and so the ideal frame saddle tube should be 48.14 cm (obtained multiplying the height at the crotch by 0.58). The frame saddle tube measures 48.5 cm. So it seems that the frame is correct for me. Do you agree?