While kit numbers have changed over the years so would have the numbers outside of the molds. Every time there was a sale of the company there was a different boss that had their way of doing the cataloging of the molds. Again with different part numbers on the releases the make matters more confusing. I would think that someplace on the large blocks is a stamped or engraved number. The problem is that it may not be in the right spot while it is on the shelf. so they Paint the numbers on the side so you can read them. Most factories I have been in the mold storage room and rack was not lite very well. Today's lights are much better and cheaper to operate.