N° 1 shotshell

Somebody set me theses pictures without dimensions.

any info ?

This is not 1 Ga shell - the primer is very big. I suppose, that she is common 12 Ga, but headstamp is interesting.

Just throwing it out there, but could the primer itself be a No.1, in a 12ga shell?

JP, this is a new empty hull made to be loaded as the No. 1 Igniter for Jet Engines, but this example was loaded as a normal 20 ga. shotshell. Regards, Fede.