Bicycle Tutor

I have a Duell steel frame. I do not have the slightest clue of what type of bottom bracket I need. Any insight on how to find out the type I need french,italian, etc. Help will be most appreciated , for my Alan frame has some cracks on the rear hangers and the Duell will be my replacement. One thing I do know is that bottom bracket that I replaced on the Alan does not fit the Duell, the bottom bracket is smaller. The bottom bracket on the Alan is a 120mm English. So knowing that what is next on the bottom bracket size chart?
Thank you for your time

I have the bottom bracket that came with Duell, it is a Campy 36x24 F. Also marked 35Nm. Could this be Italian? What desire to do is use my Chorus group on the Duell. Should I also consider the spindle length?
TY

36x24 is italian thread. 35Nm is the recommended torque for installation.
http://sheldonbrown.com/bbsize.html#threading
Spindle length depends on the crank (and sometimes the frame's shape). I believe Chorus 7-8 speed takes a 109 to 111mm spindle. I think later cranks take a shorter one. You might need to research a little more. I'd try installing the BB you got with the frame just to test fit. Even if you intend to replace it, it gives you a starting point in testing the length.