The one on the drivers door is indeed screwed on, and the one on the firewall appears to be taped/glued on in the "full rig" photos:
The earlier photo of just the tag (with smeary paint) does have rivets, and does match the frame, and does reflect an early '77 VIN...could just be an artifact...
My hunch is it's a general market rig that's been US-ified...but just based on a few things and Spidey sense.
Quirky, but seems fairly clean on the surface...I'd give the bodywork a careful eye for "lipstick", and mainly if the price is more in line with its quirks vs a premium for a...