Questions on two 20x138B cases

[US-Subs]

Trying to figure out who made them (country), and what is the reason for the knurling on the case to the right, dummy/drill?

 

[rigby]

The left case is a rare american one, the manufacturer is unknown to me.
The case on the right is a german WW2 blank cartridge case. Recognizable by the knurling, the triangle in the head stamp and the strong crimp.

 

[papyccs]

Bonjour

For right case : german, and knurling : and if I don’t say something stupid: blank.

Papy

 

[Hoeksel]

Wow, US made 20x138B! Very, very rare. The maker is surely mentioned in the great 20x138B book by "what is his name again" (hard to add value if you sold both your collection and books).

 

[US-Subs]

I still have a lot to learn in medium caliber. Apparently we tested the 20x138B using cases from at least two manufacturers.

 

[rigby]

Only these two manufacturers in the usa made these cases.
These are really two fantastic cartridges.