I recently got my first stove with external NRV. I cleaned it and changed most of the seals, the lead washer in the NRV cap was still ok. The burner seems to be original, but it was strongly twisted. I tried to twist it back nearly its original shape. No damages due to that... puhhh compared to the other stoves in the SRG I think it is from the 1930s, but I am not sure. The stove seems to be bought in Augsburg, Germany in a store owned by Hans Nussbaum. With a quick search I couldn't find any information about that store. Ciao, Bastian