Sinar bank holder thread question

[Vaidotas]

I started organizing my Sinar P macro set up, using two tripods and two Sinar bank holders and stumbled in to unexpected problem - one of the bank holders has thread, bigger than 3/8” .
It’s looks like imperial, not metric.
Anyone knows which thread it is?
Is Sinar was using odd thread on other parts?
Photos will follow if it’ll help
Bank holder is from 1985.

[Daniel Unkefer]

Some were 3/8" and some were 1/4" Bigger one is more solid fit.

If that doesn't make sense post a picture of what you have

[Vaidotas]

1/4” (smaller) and 3/8” (bigger) are common “photo” threads.
The hole in my bank holder has bigger thread than 3/8 - 3/8 bolt just sinks in.

[Drew Wiley]

Yep. 1/4-20 and 3/8-16 are international standards in photo tripod applications, and 5/8-11 internationally for surveying tripods. So you might try 5/8-11.