@Denscustom1 Dennis, that's about as logical of a hypothesis I've heard. But then you see other KTC spanners such as these with stamped numbers 29 & 17, so year of mold, at least in these cases, wouldn't hold true. But you might be onto something though. Maybe they are just the numbers of the...
Similar to the Toyota wrenches, it's a mystery. A Japanese contact actually asked KTC about those and they were pretty close-lipped. Year of manufacture was speculated, but that is likely not the case. Maybe forging machine number? Batch number? Any other speculation?
KTC (Kyoto Tool Company) has manufactured the open-end wrenches in Toyota tool kits since the early 1950's, all in metric sizes. This is a vintage standard set from late 60s to the early-mid 70s that was available from KTC directly or from KTC retailers/distributors. You can date them to the...