IMA Headstamp ID Required

This headstamp appears on a pistol cartridge that fits within the measurements for a .450 Short Revolver cartridge (and several related calibers). Anyone recognise the headstamp?

At acronym-finder they list several possibilities for IMA:
but the only relevant one on that list might be “Indian Military Academy”, or maybe “International Military Antiques” (if it is a novelty headstamp)?

I do not know if I am right but there is a IMA headstamp on shotshells made in/for Angola.
I cannot recall the meaning of IMA though.

Regards rené

Where was this found? It appears to me something I have seen out of Argentina, I am trying to locate my literature on it.