Here are some comparative photos of two Nos. 5 (there are extensive individual shots of each in other threads in this gallery): one is pre-1911, with the old silent burner R. 133, while the other has been chosen (1924: N) to illustrate some of the changes, especially the "new" silent burner design, which was announced in 1924 (this stove came with an attachment to the written instructions introducing the new model burner, R138 - later 4138) which, with minor modifications, was used through to the end of the Bjorth era in the early 1960s. Also present in 1924 is the recessed filler assembly, a patented device, to obviate the possibility of over-filling the tank. This feature applied to the pricier Nos. 1 & 5, rather than to the analogous Junior and Senior models. The inner burner caps, marked on the top in three languages (oben-dessus-up) to prevent their being installed upside down, are identical.