These are used by the manufacturer to track quaility control. They are now used to determine if the part is probably correct for the Corvette it is installed on. The date code on an engine block is typically on the belhousing flange behind the distirbutor. Distributes spark from coil to spark plugs. Controls spark timing.
Many cars have no documentation or history.
It is a good thing to have. You can check up on when modifications were done, where stuff like missing ignition shielding went, etc. If there is something atypical about the car, like a hand-stamped block, you can sometimes get affadavits from former owners that this is the original block and was never removed from the car. Early cars 1957 - 1965 used Fuel Injection that was unlike our modern electronic Fuel Injection cars of today. They often were very difficult for mechanics to adjust or maintain.