Help with Marin frame numbers please!

[Muttlemun]

@Muttlemun Have you got a picture of the number as that seems a little odd.

M is the Marvel factory, 3 is the year, but i would have expected a number instead of that first "A" to tell you the model.

Thanks for getting back to me. Here's two! Couldn't get the whole serial on one pic. Plus a pic of the bike - some unexpected components like that Club Roost stem.

Yes, I was confused because it doesn't follow any of the four patterns you highlight in the other thread.