The XN control cock would indicate pre-1940; and the black bakelite knob, 1934 onwards. So if all is original, 1934-1940 would be my proposition. It’s a lovely looking lamp and you are very lucky to have the vitreosil G10 (I think) globe (see here). Cheers Tony
The curved frame appears first in the 1936 catalogue so '34 to '35 will perhaps be more accurate. Nice old lamp for sure. ::Neil::
You are correct Jean and it would also have had the early heat deflector, the link below shows the relevant catalogue. Jean J https://classicpressurelamps.com/threads/1934-folder-no-1.2388/