Anyone for a Standard Surveying Thread?

[Spurry]

To attach a laser to its tripod is an adapter with a 5/8" x 11, referred to as a Standard surveying Thread.
It seems that it could be a BSW or UNC thread, the only difference being the flank angle of either 55 or 60 degrees.
I appreciate that it does not make a great deal of difference and either would probably fit.
The supplier of my laser said it was a BSW (as far as he knew...). My ordinary thread indicators show it is 60 degrees. (No fancy shadowgraph I'm afraid).
Overall major measurement of the several male thread adapters that I have, do not really help.
I received a length of 5/8" UNC studding today, which fits the female thread as expected.
Does anyone know with any degree of certainty what the actual thread is?
Thanks.

[awemawson]

I'm sure back in the early days that they would have been Whitworth if made in the UK. Quite probable that manufacturers have moved to UNC for their own convenience but I doubt that it makes an iota of difference !

Best search for BS standards which likely now have been converted to DIN standards.

[Spurry]

Thanks for the hint, Andrew. My searches on t'internet could not provide the info I was looking for, hence my post.
It just seems (to me ) to be very odd that there are lots of references to this Standard Surveying Thread, as if everyone should know what it is. 

[awemawson]

I found several references to American standards, and even one of the Americans adopting the Whitworth thread for this usage, but no UK ones sadly.

[Spurry]

There is a Standard for the thread set out in:   https://www.iso.org/obp/ui/#iso:std:iso:12858:-2:ed-1:v1:en

So it seems BSW lives on, but UNC will also fit. 

[Henning]

I recently made an adapter for a self leveling rotating laser and when measuring the thread it looked to me like it was 5/8”-11 UNC. My laser definitely had 60 degree threads.