Here's a view in the top.
The ceramic cap has a lovely pattern on it, probably from stuff falling in through the ventilation holes.
I can only see a single tube, and the shield on it looks pretty rusted. Oddly enough, that's all that appears significantly rusted. I think the chassis is aluminium, so while it looks a bit crusty, it seems mostly just in need of a clean.
One board there looks to be in remarkably good condition. I expect the gold playing of the PCB tracks has something to do with that.
And looking from the other direction, the various adjustment trimpots look nice and clean!
At first I was concerned about the almost unreadable meter, but that seems to be just an accumulation of dust. I rubbed some of it away with my finger.
I think there may even have been an AC probe for this. I don't have it at the moment, but looking at where it plus in, and remembering something that was also where this was found...
Anyway, I'm sure this will require serious work to get it in a condition where I would even think about applying power. Should I take it on?