I don't know much about the company, but they sold a wide range of budget electronics in the 60s and 70s. They made budget test gear as well.
It may be difficult to find those output valves at a reasonable price. I would consider changing the mains transformer to provide a 6.3V supply which will give you a range of options. EL91s are reasonably easy to find or you could even use EF91s if you don't need a lot of output power.
Don't forget to check the grid coupling caps before doing anything else
Paul