There is a notation in the USGA rules that mentions using a 60 degree plate for measuring club length. It is in the section of rules that notes maximum length of a club is 48". My reading of this is that defines how a club will be measured for conformance to the length specification and not a standard for lie angle. Thanks for the comment. It has inspired me to write a lesson about USGA club and shaft conformance.

@@DevotedGolfer Like anything else in golf - no standards. But it has been kind of excepted as "standard" in the last few years. OEM iron length is another w/o a standard - they all measure club length to a different spot on the grip or w/o grip. NUTS