After restoring my Prentiss Wabers No 8, I had my eye open for something similar. I found a Preway, same company, in the 4521A model. It looks like it has seen light use. It required very little from me. I washed it a bit and pressure tested it. No leaks showed up but the NRV in the pump allowed the pump shaft to stand proud. On this model there is a pip that is accessed from the outside of the removable pump. The spring seemed very weak so when I dug out an Optimus pip I tried another spring. The pip fit perfectly but the spring was too strong. So I slightly stretched the original spring and it seemed to solve the issue. I really like this little double burner. It seems to be from the 1940's according to more knowledgeable people.