I was just looking at the Remington Model 8 magazine. It's a John Browning design with an interesting trick.
The lips on the magazine have to be tough enough not to bend or wear. OEM carbon steel magazines use specialized heat treating. Cheap magazines (like the original RPB magazines for my MAC-11, and some 1911s) are just bent soft sheet metal, and eventually wear or spring out and then fail to retain the cartridges properly.
JMB's Model 8 magazine is ordinary sheet metal as far as I can tell... but the lips are spot welded on separately. They're tall and are attached to the bottom outside of the mag.
Besides simplifying adjustment, it means if you make a mistake when scratch-building a mag, you don't have to throw all your work away; you just weld or rivet a new pair of lips on.
This page is about the Krieger removable magazine conversion for the Model 8, with some excellent pictures of the mag, which you normally can't see.
The Great Model 8 & 81 » Krieger Detachable Magazines