A reasonably decent 'user' example of this relatively uncommon stove, on the right above. For scale on the left is a standard No.5 stove so it can be seen that this version of the No.21 is larger, but not as large as a No.2 despite sharing the same size burner. This 1930s/40s iteration of the No.21 was the roarer brother to the more common No.25 silent burner, and nothing at all to do with the pre-WW1 discus No.21. Found as an abused cast off, it had been fitted with a No.5 silent burner and abandoned because "it wouldn't pressurise". The latter problem turned out to be due simply to a blocked NRV and an incorrectly assembled pump! Obviously both very easy fixes. And now it has been treated to a correct size Liberty brand roarer burner to bring it more or less back to original specification and power output.