Lew, I also have a Walker-Riemsdyk in the collection. It doesn't quite have the heft of the Walker-Fenn, but it is a fine running locomotive. Different type of adjustable governor than the W-F as well:
I have a 1953 W&H catalog that advertises the locomotive - here is a scan of the page:
The only other clockwork I have with an adjustable governor is a Bassett-Lowke, but it is a future project that is in pieces right now.
EDIT: Your shell looks like the one on my Walker-Fenn. I have heard that the W-F used a Marklin mechanism with the addition of the gramophone style governor, but I don't know if the body was made by Marklin or W-F (I thought they made their own - not sure). I wonder if the W-R locos used leftover pre-war bodies postwar on their own mechanisms before going to the style seen in the 1953 W-H catalog. Of course, the other possibility is that someone with a pre-war W-F acquired a postwar mechanism to power it. Hard to say...