I think I know what your talking about John but haven't a clue, sorry.
I did find this...
1 lb propane tank:
The thread size of a 1 lb propane tank is 1/4”MPT. This is a universal size for all 1 lb propane tanks. This fits all kinds of bottles, hoses, and regulators. Therefore, this is an ideal thread size for a 1 lb propane tank.