If the dates are July 16 68, they may not have even went on a production 68 z/28 and may be a service replacement wheel. That would lower the value, IMO
These wheels (and the other sets I mentioned) are all off production cars. This guy is super meticulous (never married, no kids, same job for 30 years, spends his lunch hour at the auto salvage yard next door, etc...). Anyway, he has every part labeled with:
The date he pulled the part.
The make, model, and production date of vehicle he pulled it from.
Price he paid.
Anything else he feels is relevant.
The service replacement wheels were available after '68 Z/28 production was complete and therefore are date stamped accordingly. Like this one:
There are other differences between the production and service replacement wheels all covered in detail in Jerry's '67/68 fact book.