I'll expand this since it is not getting any air play on access norton. They are a fairly dim witted bunch.
These "made in England" sprockets are made by Dave ? at Vellocete. I started getting some as much if not over 5 years ago from RGM and more recently as 2 years ago from BCS.Andover Norton is reported to sell them also I have a stack with 18teeth, 19t, 20t, 21t, 22t, 23t, 24t. Every one of them plainly marked/stamped "Made in England" as the only marking.I have now hardness tested them all, and all are soft as butter at RC 15 to mid RC20's.
Contrast that to another stack of OEM original Norton factory take offs. I harness tested them and they are all in the high 50's and up to mid 60's Rockwell C...which is hard as tool steel.
On a secondary note: BCS is going to send me a "EMGO" sprocket for harness testing. I can hardly wait...