[Arran]

 The chassis for the 41-290X and the 41-280X are almost identical, in fact in my Philco service manual for the 1941 model year the only difference was the addition of a separate detector/avc tube, the 41-280s used a 7C6 but the 41-290 added a 7A6 in addition to the 7C6. The only purpose that I can think of for this was to boast that the 41-290 was a nine tube set and therefore a better radio, but in reality it was basically an act of tube stuffing rather like what RCA used to do by adding a 6H6 to a radio rather then using the diodes inside a 6Q7 for the job.
Regards
Arran