It looks somewhat similar to the type of stuff used by the old Postal Railway clerks. It probably didn't sell for more than a dollar when it was new, back in the day. It looks old, maybe 1910-1930's? Here's a photo of a 1964 U.S. Postal Service contract holster.
They were typical generic designs of the day. Like the collectable Victory holsters, it has the rivet ends at the mainseam. The was common practice before the improvement of double row stitching became popular, especially on open muzzle designs. Brauer made many of these type, but so did many others. To keep prices lower and labor less costly for contract runs and price concious retailers, it was cheaper to single row stitch and rivet. Note in the top photo it is copper riveted & burred by hand set. Yours is rivetted with a splash anvil rivet.
They weren't high quality, but got the job done I suppose.
The postal service also used a 1917 flap style holster during the 20's. I think they were made by Millsco. They were pretty good quality and are collectable today, no doubt.
Nice score on the P-38!
Cheers;
Lefty