Tube question - who makes Magnum Dynalab Reference 6922 Cryovalves??

6922s are very plentiful, similar to 6DJ8 and 7308. If you want reliable sources, I’d suggest RAM Labs, Jim McShane, Antique Electronic Supply, Kevin (can’t recall last name). I have left out other reliable sellers, but don’t buy off eBay unless you have independent evidence that the seller is honest. Some of these sources will do cryo, if you pay a bit extra.

Think they used cryo'd tubes from various manufacturers.

A quick Google search found mention of Phillips USA and Russian 6922's (both of which used to be plentiful/inexpensive).

If you can post close up pics that would help.

Otherwise look for the Tubemonger tube library website as he has excellent pics of various tubes, including 6922's.

DeKay

Several years ago, I owned an MD106T and purchased the cryovalves directly from MD.  They were nice tubes, but I think a little overpriced.  At the time I think they were using Electro Harmonix or JJ.  

Instead of guessing, why not send an email to Magnum Dynalab and ask them? They are very responsive.  Enjoy your FM.

I strongly doubt that any real tube manufacturer ever cryo-treated their product.  In my experience, that is always an option occasionally offered by the better tube vendors.  But I am always willing to learn something new.