Originally Posted by
howieleem
I saw the Sheldon website too, so am i right in thinking that if it is 68mm it must be the Std British?
Not quite. If the shell is 68mm wide, it
might be more likely to have standard 1.37 x 24tpi thread, but you can't be certain until you've threaded a known 1.37 x 24tpi cup into it.
There was a lot of variability in parts in the past. I have a number of British frames with 66mm, 68mm, and 70mm shells with 1-3/8" x 26tpi thread.