30 vs 9mm AM III magazines?

Recently this was noticed in a photo I posted (this is an enlargement):

The magazine on the right was one of two that came in the box with my like-new AM III in 30 Carbine and the one on the left I bought as a spare. Somebody here said one is a 9mm magazine, differentiated by the different angle on the end of the follower. Since the two that came with the gun are like the one in the right I assumed he meant the one on the left was a 9mm magazine. 

Comparing notes with John Lodahl, he sent me pics from his collection:

The mags on the right have a follower with a flatter profile at the end and are purportedly from 30 carbine guns. The one on the left has a black follower and is from a 9mm gun. 

So, what’s going on here?  My initial thought was that the one with the longer flat portion of the follower was a 9mm magazine based on what was pointed out in the other post. But my 30 magazine followers have the same shape as John’s 9mm follower. 

Given that the magazines are all unmarked, what (if any) is the distinction between 9 and 30 magazines?  Or are they all just the same, and the different follower shapes are an early vs late production thing? Or did my 30 Carbine gun just happen to come with a pair of 9mm magazines by mistake? (The seller had numerous AM IIIs and could have mixed them up).

Please, educate us if you can!

I’m still confused. We are talking about two different shapes and you refer to ‘that’ without specifying which you are speaking of?

The top magazine in the pics above has a shorter base and a longer flat front on the follower. Are you saying this is what the 30 Carbine magazines looked like, and the 9mm magazines had the longer base and shorter flat section?

Or did the 30 Carbine and 9mm guns all get the same magazines, and the magazine design changed partway through production, so the issue is early vs late instead of 30 vs 9?

My 30 gun came with two magazines of the long base/short front variety…and it seems to feed and eject fine?