Help me with a Fidelity Research FR64 part

 Based on my prior experience with re-tooling for Fidelity research and technics products, I guessed earlier that it is metric. 25 threads per inch is just about one thread per millimeter, which is a standard for metric. The thread pitch is 1.0. Of course, I am not there, and I am not a machinist. I don’t want to step on his toes.

Most of the machinists i have met are not interested to make just one small part, it is not interesting for them and they are busy with some serious orders. Unfortunately we're not their customes with one nut or one screw or anything like that (cheap parts).  

As I mentioned at the top of the thread (I think), I DO know a machinist who most likely would make this single nut for the OP, if he is given the correct specifications to work from.  That is Colby Lamb in Oregon, USA. I can provide contact info, if desired.  Colby made me a new threaded retaining ring for my SP10 MK3 platter; without that part it is impossible to fix the platter in place.  It sounds like the needed FR nut may be M30 (30mm diameter) with a metric pitch of 1.0.

this thread is turning me absolutely nuts - some may think I am unstable :) 
24 and 26 TPI is quite standard 25 is not - trust me I searched... Also bear in mind the odd diameter as well

Parrotbee
Most of the worlds population work with the metric sysrem. The population of Japan belong to this club
As Lewm suggests, this appears to be a M30x1 thread. 
It is defiantly a standard thread. 

Neither the thread pitch or diameter are unusual outside of USA

cheers