Unknown .45 rimfire?

I have been asked to try to identify the cartridge shown here, but am having a difficult time with it.

The owner has indicated that it has a copper case with flat nose lead bullet with 2 exposed grooves. It has a roll crimp tightly seating the bullet in a groove. Bullet extends .60 out of case.

Case Length… 1.10"
Overall Length … 1.720
Case Diameter at mouth… .451
Bullet Diameter at mouth … .45
Rim Diameter… .510

Any help would be appreciated.

The bullet on this cartridge has a very ‘Danish’ look to it, but the dimensions don’t match any of their rimfire cartridges that I’m aware of.

I was asked to get the weight of this cartridge, and requested that the owner check his measurements. I got the following:

WEIGHT 24 Grams (Electronic Scale)

Case Length 1.16
Case Dia above rim .455
Rim Dia .529
Bullet Dia at case mouthy .448
Total CTG length 1.716

That change in the rim measurement pretty much settles it for me; as suggested by the fellow who requested the weight, I believe it is a .46 Carbine. The bullet is not like any .46 Carbine bullet that I have seen before, but perhaps this was a primed case that was loaded outside of the factory.