I have all three (Patent, Brev. Camp., and nothing) on my various brake center bolts, not sure if "Patent" came before "brev. camp." That's MY guess.
My "Patent"s came with Old Logo (Sunshine) hoods, straight QR's, old steel wheel guides, and brake lever handles with the engraved "pivot," etc (in a dusty box, which I love!), so I'm guessing from everything I've seen in my 1973-1977 Bicycling! Magazine Collection, that they are period correct for mid-70's.
Now brakes could be the exception to the rule, but most of the other parts (pedal dust caps, chain ring bolts, etc) that have a "Patent" are up to mid-70's (1977?) and "brev. camp." is 1978 - early eighties (after the CPSC forced 'safe' components). "No marking" center bolts is when it all started going down the you-know-what... 1984 I believe.
Love to hear from others to confirm or deny these findings. The cranksets and NR/SR derailleurs are so easy to date, too bad the rest of the components are not as simple...
Bruce VR- "old-logo'ed, bumpy-levered, steel guided, number in a diamond" Campagnolo-Lover (Phil Wood is cool too!)
P.S. Oh yeah, I too prefer the SECOND (of 3) generation "Rally," although it can't be opened up like the non-reinforced version a few years prior... but who ever did that anyway?