Wow, cast the day before it was assembled? Would that normal for a DZ? There's a couple things I don't like about it, but I'm not a stamp expert so I'll leave it alone.
My Z28 has the original 302 which was cast on 27 Aug 69 and assembled the next day! Probably NOT normal, but these things did happen. (I have a totally original '57 Chevy with 283 engine which the engine was assembled the SAME DAY as the block was cast (it must have been cast in the early morning hours and assembled much later that day, but seemed unbelievable to me when I purchased the car in 1978...
Gary W / 09C 69Z28-RS, 72 B 720 cowl console rosewood tint
69 Corvette convertible, silver/black 350 hp,
60 Corvette white/red, 72 Corvette coupe, '70 Mach I
90 ZR1 red/red #246, 90 ZR1 white/gray #2466
72 El Camino, '55-'56-'57 Nomads, '55-'57 B/A Sedan