I must admit my error, when I read Dreyer, I was thinking Dewar. A dewar is of course an insulated storage vessel that you can store LOX in. With the reference to high pressure, this clearly makes the system being described as gaseous.

Wishing to look a bit further into it, I had a look at AP388 published in 1921, it describes all the systems then current, both liquid and gaseous.

They had got to Mk IV by then for liquid oxygen vaporizers and high pressure delivery regulators.

It seems a lot of development was made in the late and post war period.