I am no expert and will likely be corrected by the more knowledgeable but, looking at the spares book, the first year to list an oil purifier was 1931. The cupped plug was part 1077-31 and a centre tube 1075-31. There is a different plug listed for 1933 onwards namely 1077-33 along with the same centre tube 1075-31 ion pre-war singles parts books. Whether the centre tube was used on all models I don't know as there is a note "not red hunter" on part 1075-31. Post-war parts books only list the cupped plug and not the centre tube.
I hope this helps answer your question but I'm sure the exact chronology of Ariel oil purifier will be forthcoming from those in the know.