My first metal lathe was bought new in 1954 and had 3/8-24 feed screws on the cross and compound. But it also had no dials, so there was no confusion trying to read dials with strange numbers of thousandths on them. Proper lathes do have dials and feed screws with pitches that allow more or less convenient numbers of thousandths on the dials, like 25, 50, 100, 200 or 250. I have machines with all five of those dial types.
So, like Steve said, pull the screw out and see what thread you have. I have seen very worn feed screws with no hint of the original thread form in the worn portion. Even then, the original pitch is easy enough to measure and the thread form is still intact at the ends.
Larry