Help me identify an amp

Fantastic, thanks to everyone for helping! He often mentioned Dyna to me (we were also both interested in Sunn bass amps, which are based on a Dynakit design). Is the ST70 something that was sold as a kit? He may have assembled this himself if so. I will try to open up the chassis later and see if the PCB has any marks on it. 

While I’m at it, I may as well ask my next question: what is it gonna need to get up and running again? It certainly hasn’t been used since 2012, probably even longer.  I know electrolytics fail with time. Given the usefulness (not to mention sentimental value!) of the gear, I will definitely want to take it to an amp tech for restoration. What should I anticipate needing to do?

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  

Thanks again to everybody for all the advice. I will look into acquiring spare tubes and study how to power on safely with a variac. It's possible there's one among my father's things, as he was very fond of tube hi fi amps, as well as vintage guitar and bass amps. As for the schematics, I really appreciate that, but I read that there were multiple versions of the GSI mod, so I'll have to check to make sure that matches the circuit in the amp. It seems that Andy Fuchs, the guy behind GSI, is still building amps in New Jersey, so maybe I'll contact him with any problems.

Sadly I'm not at the old house that often, so I may not be able to hook up the amp or test it for a few months. I am looking forward to trying out the entire rig, though. Apart from the Dyna power amp, there's an Audio Research pre, a Linn turntable, and some homemade woofers that will be a pleasure to try out.