Help ID Toilet

Just yanked an older toilet, with the following markings:

A large blue K between the seat and tank

inside the tank a K4524 above a 70973 and a red stamp F-25 (inspector?)

under tank lid K4552 above 7973 and a large 3.

Anybody have the decoder ring?

Those are Kohler numbers.

I was able to Goggle the tank lid number.
How old a toilet is this?

Not really sure, original homeowner lived here for 40 years, however, the toilet is elongated (not sure how far back those date) and it had a plastic nozzle on the wax ring (not sure how far back those date either). Also had the fluidmaster 400A fill valve and it had a flush valve seat repair. House was built in 1960. Found about 1/8" of hard water deposits in the trapway which was probably the reason it flushed poorly.

The 1/8" may not have made a difference, but a similar amount in the part between the tank and the bowl probably would - it would have slowed the amount of water dumping and the bowl wash. My unprofessional opinion! There's a big difference in the quality of flush on new toilets, and there are old ones, even with a huge water flow, were junk, too.

ceramic date

The ceramic date is molded into the china like the kohler number.