[Collins] set screws for ring gear of 75A4 dial vernier

[John King]

I have lost the two setscrews that hold the ring gear on the shaft of the vernier knob assembly of my 75A4.

I need to know the diameter of the set screws, the thread number/pitch 
and whether the set screws are Bristol or Allen drive. Any identifying 
information available will be greatly appreciated.


If you can, please provide me with the needed information and suggestions  from where the two set screws might be acquired.
Thanks for your assistance. 73, John, K5PGW