looks lovely and original to me

my K was originally cadet blue and had horrid dark green house paint over it. I loved the cadet blue that was in the boot though...
some will tell you the ID plate should be stamped from the back, but I've seen a lot of cars with it stamped from the front like that. I reckon the rear stamping was done by a machine, and the front stampings done by hand when the machine was broken. Those ID plates were introduced in January '70, and your car being that month (cool!) it may be one of the first that got the ID plate put on it.
The number on the radiator shroud should match the ID plate, and should have the prefixed YG2S1, yours might not have been stamped, or may be covered up. If you can get your finger under the shroud, or use a mirror, you might find it.
The number on the firewall should be behind the clutch master cylinder, just below the paint code sticker. It may have been missed, or may be covered up.
Also have a look in the passenger side of the channel at the back of the engine bay (where the rear lip of the bonnet goes when you shut it), the car number might be stamped in there. I've only ever seen a couple of cars that had it stamped there, and none of mine have had it.
45 years ago when these cars were sausages being pumped out of a factory, not all of the employees were "fully engaged" in what they were doing - some cars have the wrong numbers, some numbers upside down, some stamped from one side of the car and others from the other side of the car, and all sorts of weirdness. Don't get too hung up on it...
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