Help me identify an amp

Mystery solved: the PCB says GSI on it; however there appear to be different versions, so I will keep digging around. It’s likely my dad saved the documentation somewhere.

I will look up Will Vincent. Thanks for the recommendation. 

Jerry, thanks for giving me a chuckle. Everything is shoved in different parts of the house ever since Hurricane Sandy. I’ll get around to hooking it up and testing it out one of these visits!

Thanks again to the community  

Carlsbad2 - Absolutely Not!!! Never ever do that with vintage tube gear unless you want to risk replacing an expensive and hard to find transformer.

Bring up the voltage slowly on a variac is the right thing to do.

so it may be a GSI modified Dyna Stereo 70 that uses 8417 output tubes

+1 on the variac and nice and slow you don't want to fry the amp especially transformers which are the best part.

connect some speakers, any load, when you power up tube amps

+1 variac - to bring up power slowly/safely to see if working, especially for tube type amps.