Does anyone know about the threads used on early Zeus frames
I recently bought a 1960's Zeus. It has Nervex Pro lugs, and had a mix of 1960's parts on it that make me think mid-60's.
I have now taken the original Zeus BB cups out - thankfully neither side was seized, but the cups are not marked with any thread info.
Here's the weird thing - both sides are a right-hand thread, and they appear to be 1.37 x 24T. The drive-side cup is exactly that - two spanner flats on a fixed cup (no lockring)

I can thread other cups with that thread into either side - Are other thread sizes close enough that I could have this mixed up?

Has anyone ever struck this - and where can I find a replacement as this one is quite worn?
Thanks from Mike in New Zealand