Thanks for the add guys! Hoping you can help me (and Lego) out here 👍
I spoke to Lego and... They confirmed that this is an original Lego part, but that they don't have access to any records or background info for it such as whether it was a prototype or an error, what factory it was from or how many were made.
***EDIT - Another update from Lego (maybe because I didn't reply in time, they are very efficient 👍) "This is an older, discontinued part and I do apologize, but we do not have access to any records of this being made at this time."*** Very sad that there's been at least 8 moulds made and they only know of 5.
The entire inside/base mould of this one is different to any known ones, with a larger hole in order to accommodate the extra plastic and the metal ring. The patent for the wheel 7039 was still pending when many of them were released so it's possible that this was a prototype that was too expensive or difficult to make large scale, and the records of it being designed and made are lost to Lego, but I'd love to actually know for sure. (I have heaps of them that just say 'pat. pend.' inside instead of a number.) It's been speculated on other groups that it could be a high performance version, an attempt to prevent the cracking around the axle?
It seems based on a known wheel (7039) that has at least 8 variants, but this isn't one of them. I have some of each of these variants:
-extra circle around the logo on each stud,
-chrome axle
-cam axle
-bronze axle
-teeth w/ chrome axle
-teeth w/ bronze axle w/deep, angled notch
-teeth w/ bronze axle and shallow notch
-teeth w/ cam axle
-melted marks (this is displayed as a variant on Bricklink but I'm wondering if it's a type of damage? Does anyone know?)