I got this cartridge about a year ago, but have never got round to posting it until now.
It is a brass cased .50 BMG dummy with no headstamp.
There are four equally spaced holes of around 4.5mm (.18") diameter and 39.5mm (1.56") from the case head.
The bullet is a standard steel-cored, GM jacketed NATO M33 ball.
The primer pocket is 7.9mm (.311") diameter, and 4.94mm (.19") deep.
Thanks in advance for any info.