CD - I've been reading a bit about them, and it seems like they may have made some of their own machines, and then they started making them for others, and at some point they were acquired by another, and basically absorbed, but they still used them as the "name" of the mfg of the machines.
All the White machines that have AG Mason on them are made by White (or for White), but it sounds like there may be some earlier machines that aren't quite the same as the White ones. I think one of the few ways to dig into this will be to start looking at advertisements in the Smithsonian records - but most of them aren't online at this time.
I find it all fascinating - and each time I start looking into something, I find other information. There is a lot of conflicting info - and a lot where it's speculation based on items found, but no one will ever know for sure as the actual records are gone.
Most "history" books I've encountered don't spend much time on the 1900-1930 era machines, but concentrate on the earlier years.
And just when everyone thinks they've got a grip on something - a machine no one has seen before shows up, and it makes everyone wonder . . .
This Queen is one of those - it has a lot of marks for White, but also a lot that are different, and there aren't any other similar models either. So no one knows for sure if this is a machine made by some other MFG using some of White's patents - or a machine made FOR White by another factory as a "test" . Several companies stopped making their own machines (closed their factories) before they stopped doing business all together.
Maybe if I'm still interested in all this when I retire, I'll have fun researching it. Right now I'm just having fun finding out what I can find out - and I know I'm not an authority, but we're just all machine enthusiasts here, and it's ok to have fun guessing and the like. it's not like someone is going to be financially ruined by it. Well, unless they get addicted and spend all their money on vintage machines!