Hello Rob,
I guess I am bit late to reply, but I just came across your posting.
In case you still have the scope here is some info that might help you.
Your scope looks just like my Iwatsu SS-5702 scope.
I suspect it is just a different sticker on it.
The scope is more like early '80s.
The manual is available on the web, but I also have my original manual.
If you can not find it, as free stuff seems to go away these days, and replaced by all sorts of "downloading programs", send a PM, I can send you the manual.
I also got my scope in the early '80s, second hand, but it was barely used, only about a year old. The guy originally paid about C$850.00 for it, I still have the original bill of sale.
The scope has been working fine ever since, only thing is that lately sometimes I have to exercise the AC/DC/GND lever at the input.
Now I have other scopes as well, but this scope is still on the bench!
Regards, Peter