I left a couple of things out. What is the threading on the bottom bracket cups? English is desirable, Italian less so, French much less, Swiss not at all. Another biggie is the pedal threading, English threads are what people want, if it has French threads it is a bit problematic. The pedals can be tapped from French to English but you lose the rear side cap from the arms so collectors will have less interest. If the bottom bracket is french then likely the pedal threads are french.
Codes for telling what the bottom bracket threads are:
threading marking on cup faces
French (35 x 1.0 mm, right-hand thread fixed cup) single ring around spindle hole
British.ISO (1.370 x 24 tpi, left-hand thread fixed cup) double ring around spindle hole
Italian (36 x 24 tpi, right-hand thread fixed cup) no ring around spindle hole
Swiss (35 x 1.0 mm, left-hand thread fixed cup) single ring around spindle hole, "G" stamped on fixed cup
marking on lockring edge
French 35 x 1.0 mm, XXXXXX
British.ISO 1.370 x 24 tpi, ||||||
Italian 36 x 24 tpi, //////
Swiss 35 x 1.0 mm, XXXXXX