This is an example of the original German version of the Ehrich & Graetz 'Virtus' stove that was also sold under some sort of license in Britain as the Falk, Stadelmann 'Virtus' in the early/mid 1920s(c/f). Unfortunately, as with the Falk's version linked to above, this one is missing its original distinctive burner(see here), and is now living with an unbranded standard roarer. The distinctive green of a burner not fired for a long time time, but it clears quite quickly:
Excellent post Ian, a great example. It's fair to say however, you well and truly fell off the patina wagon with that one! Alec.