According to my info all reissues had 4 digits and aftermarkets did not have have GM part numbers on the horn.
Holley has also made (and still makes) re-issues with a GM part number and no date stamp so their resellers can date them to their customer's needs.
Who sells these re-issues?
69 Z/28 Dover White X33,ZL2,PS,M20,Std.int.04C
67 SS/RS Mt. Green 1W,2LGSR,3SL,4K,5BY,07C
70 Nova L78 Blk. Cherry,Sandalwood,M21,02B