Not sure if the link will work :/
First post here.
This mag looks to be a new 20 rd, but with a nice shiny finish, not the matte look that you see everywhere. It looks to have three pins in it. I can't find it online anywhere.

Can't tell much from pic.

Hard to tell. To me it just looks like a used magizine that has been modified to limit capacity.

Had to link your pic to the actual image not the gallery page.

Hmm...okay, well thanks everyone :)
Do you guys know of a brand of magazine that has the shiny stainless look rather than the matte finish?

 

Back in the 70s or 80s colt toyed with a different finish called colt guard and some rifles were finished with it I believe it was some type of nickel finish.  I believe the rifles were shipped with matching colt guard magazines.

I got a magazine like that when I bought a new ban era Bushmaster back around 1999 or 2000 (one of those A2 carbines with the perm pinned "AK Brake").

It looked like someone took a 20 round magazine, squared off the bottom and pinned a limiter inside using two or three silver finished cross pins. The mag body wasn't shiny, but rather a very light gray parkerized finish (that was super thin, I remember the magazine scratching super easily). The floorplate was black and had a Bushmaster snake logo on it if I remember correctly.

I don't remember what happened to that magazine. I think I sold it along with the rifle it came with a long time ago.

Yes, it looks like a Bushmaster. But Bushmaster usually has base plates with their logo on it?

I have a couple (circa 2001-2002) direct from Bushmaster with blank floorplates and the 3 rivets.

I did an old 20rnd mag like that.Basically just scrubbed off the old finish and lubed it. nothing special like in the link.

That looks like the mags that came with my ban-era Bushmaster CMP rifle.

Found a pic: