Help Identifying .50 Caliber?

[BestPlot]

Hey ya'll! Hoping you can help me figure out what I have here.

This specific amp came to me through an old guitarist in a band I was in 10 years ago. He never came to pick it up after quitting the band leaving it at my place prior to a cross-country move. It looks... similar to most other .50 Calibers I've seen online, but in nearly every forum, including this one, everyone usually identifies the ".50 Cal" vs ".50 Cal+" (or even against Mark III's) based on the plastic rocker switches and tubes. I've confirmed there are EL84s here (yeah, I know they need replaced, and the whole amp needs quite a bit of TLC), but the metal switches, combined with a footswitch option and only a single row of tone/volume controls, is really throwing me for a loop.

On top of that, there's a Black Shadow Celestion speaker that appears to have come stock (although I could be wrong).

I've looked around online for a few days, but unfortunately I keep coming up empty on what specific make of .50 Caliber this is. I've been able to find ~2 other pictures online, but they're from ~10 years ago.

I'm interested in learning more about it. I was considering selling, as I'm about to make another big move, but the more research I do, the more I think I have something special here. Any help, insight, schematics, etc. would be greatly appreciated!

 

[electric mayhem]

You have the original .50 caliber. It was short lived and many of those amps were also short lived due to the super hot bias on the 4 x EL84's that toasted the PCB's the sockets are attached to. Not all the amps were toasted but red plates were a rage against the machine.

As you can see it has the class A EL84's, no lead master, and yours has the optional EQ. Personally I would pull the chassis and have a look at the PCB for any coloring.

Re-setting the bias for not greater than 100% dissipation or running cold tubes would tame this fire breathing dragon which could still be an impressive Class A beast.

It may have originally come with the 1st version of "vintage black shadow", the eminence VS-12.

The plus for this amp means they ditched the over-biased EL84 experiment for the venerable 6L6GC pair and made an attempt at making it a 2 channel (lead master). They nailed down the 2 channels in the dual caliber line.

 

[tommyhawk13]

My .50 Caliber is from this era. My Celestion C-90 Black Shadow was stock, built in 1987.
As Electric Mayhem said, no lead master, and metal toggle switches make this the non "plus" version.
You can remove the chassis fairly easily. Disconnect the gray reverb wires and the speaker cable, and there are 4 phillips head screws on top of the cabinet that hold the chassis. It slides out of the back.
There should be a handwritten date and initials written in sharpie on the inside of the chassis.
Mine is still running strong, and it rages even with a 12AT7 in V1.