I was looking in to another amp the other day using Fullmusic 2A3s and I was immediately reminded of sophia's. I'd totally believe that an OEM arrangement could exist. I'd imagine getting into the manufacturing side of an niche technology would be costly if you weren't already in on it. I figure the machinery used to make valves probably doesn't exist as 'off the shelf' box solutions (as it were). If someone wanted new gear, you'd probably have to have a engineering firm scratch build you the equipment. Even Sophia's site emphasises a 'research orientated' company. So they're using someone somewhere for the legwork.
If it helps anyone, Fullmusic have some pics.
http://www.tube-fullmusic.com/products/en-product.htm
If you're cynical, OEMing is just rebadging. In the short time I've been using tubes, I've read a lot about how some will chase down a particularly type with the knowledge it's brand X by any other name. ODMs are interesting too
http://en.wikipedia.org/wiki/Original_design_manufacturer