Congrats! ...looks well used and loved and modified. the blackface faceplate is a good indication someone's been changing stuff.
Some folks would run them (rebiased of course) with two power tubes to make the volume and break up a bit more manageable.
I would definitely have a skilled tech take a look when possible. Steel guitar players liked 'em for the clean volume.
The power tubes look like (newer) Tung-Sols by the color of the base. And the knob on the back is interesting and not original. maybe a master volume?