I'm just finishing off a pair of Bialaddin T10's and noticed a slight difference where the top of the font meets the riser tube. One is a straight connection to the font while the other has a small collar around the connection. I'm guessing that the 'straight connection' would have been made in the initial production and the design was later modified to include the small collar for strength? Can anyone shed any light on this? My other T10 question is about the hoods. Did the slotted hoods appear first and then a transition made to the hood with circular holes? Any time line on when this may have occurred?
Well spotted and my example of a T10 is the same as the one which is shown in your second image, the link below shows a book which has relevant information. Vapalux and Bialaddin Pressure Lamps by Ian Ashton | Blurb Books UK
Looking at a variety of things, including the gallery I would say slots first and holes later. The reinforcing ring you picture I believe would be later, as you surmise, because the T20s have them as does a 1954 T10 in the gallery but the presumed early T10s in the gallery don't.
In the Gallery the 1954 T10 is holes but the abt 1952-53 T10 is slots. I think the ones saying 1951-56 are just giving the range of years that this model was made. According to the Vapalux book by Paul Ashton on p36 slots came first. @paul m
Just for interest in the Gallery there are 16 T10s with one post having another persons T10 photographed. 8 are slotted and have no 'collar'. 6 have holes and a 'collar'. 2 may be transitional with slots and a 'collar' (one of these from @Darryl Durdin looks like it has the 'collar' but I am not 100% certain.) Since the 1954 unit from @pete sav is dated at 1954 and has holes and 'collar' it may give a way of dating some of these table lamps within the existing 1951 to 1956 period. Interestingly too is that the three that seem to have been found in Australia are all slotted. The ads I can find in Trove for them in Australia National Library are are only 1952, 1953 and a couple up to August 1954. Just a thought re possible dating of these unusual shaped lamps. PS Does anyone know the proper name for the reinforcing 'collar' referred to by @Scott M though it may well be the proper name. I have searched and cannot find an answer.
