I recently picked up a Dual Tone SVW 45 Pistol in the d block. Very near the end of the war. Inside I find the coolest magazine. I can't find any information on this type of follower.
Reminds me of those reduced thickness C-mpu marked stripper clips for the K98, very cool piece never knew these existed. mauser99 makes a good point, this is the exact reason we see ribbed Mp40 magazines begin to appear as well.