There's a Hercules on Ebay (UK) now with the same chainring and what is purported to be a '30's three speed derailleur with a pretty top tube shifter (trevelox) and those characteristic Hercules lugs. Components painted black, and marks of black paint on chrome are likely to have been a WWII blackout precaution. So I guess there are features, such as that chainring that ran through many years.