Firearm of the Day.

[DrHenley]

Originally Posted by Gatorade

The Super A and Super M were produced concurrently in 9mm Largo and .38 ACP. The two differences in these models is an enlarged breech face on the Super M that will allow the semi-rimmed .38 ACP cartridge to fully chamber
http://9mmlargo.com/star_spr/index.htm

I wasn't really that familiar with 38 ACP (I thought that might be a typo at first) so I looked it up.
One of JMB's creations, of course. Would have been the standard 9mm if it hadn't been eclipsed by the 9mm Luger.
It's actually still with us in the form of the 38 Super which is basically just a 38 ACP +P. Same case dimensions but stronger case.