Need help identifying an Ampeg...

[dennisflemming]

All - I'm looking for some help from the community in identifying an old Ampeg amp my dad bought at a yard sale back in the late 80's for $50-$75 bucks.  The speaker looks to be a 15", but the back cover says it's an M-12 model.  My guess is that it's an M-15.  I'd appreciate the help so I can figure out what to do with it.  It powers on, but trips the GFI outlet after a couple minutes.  I was able to plug my guitar in and strum a few chords, very clean.  I played the amp a bunch many years ago, but it's sat for the last 10 in an attic.  We had a family friend, an old RCA tech/engineer here in South Jersey, that did some work on it in the 90's (replaced the cord and a tube or 2).  Looking in the cabinet it really looks mostly original, even the Jensen speaker.

I took a bunch of pictures and put them in a OneDrive folder.

https://1drv.ms/f/s!ArqNHjOimf0sgcAlY5pP7kXjXU1Oqw

Thanks,

-Dennis