At first, these look like regular old LEGO IDs. But they can't be...
- Part ID: The type of part it is
- Mould ID: The Mould that printed it
- Copyright: The LEGO copyright statement.
Obviously, there is no copyright statement in this piece, so we'll have to rule that out as a possibility for the "dogtag."
We might be out of ideas as far as lego meaning here...
But Wait! Lots of plastic products have these "clocks" on the bottom!
Check out this link on SE: Seasoned Advice!
This is the date the item was manufactured. The upper dial gives the
year, the middle one, the month.
Perhaps this isn't particularly correct, because of the difference in increments, but we might be a little closer. Is it possible that LEGO is just following the plastic printing norm?
Or it possible that these numbers are made to be combined? Maybe these indicate a year or some other time, but maybe...
Maybe they're related directly to the plate piece ID somehow!
As for the 'tag, your guess is as good as mine.
But here's a thought:
The bottom indicator could be a mold identifier, and in some cases, it might be a shift indicator
Perhaps this is some sort of grahpic ID instead of a number that indicates something about that kind of mold, or even something about LEGO itself.
I spent maybe 5 minutes staring at my baseplate collection, and they all seem to have one, including the vintage models, so I'm going to lean towards a "kind of mold" instead of "a particular mold."
So here's the TLDR.
Though the internet and my LEGO friends don't know, I think we can narrow the possibilities down considerably:
- The markings mean something about when the piece was made.
- At least one of the markings means something about where the piece was made.
- The markings mean something about what the piece is (ID.)
The fun is in the search!