Chainwheel on Crankshaft

[47p2]

I have a couple of what looks to be timing chain sprockets but am unsure if they're for the P2.
Looking at the Rover parts list, item B7 part number 03013 looks to be a double sprocket of one piece and what I have are two single sprockets.

Each sprocket has 20 teeth, an inside diameter of 35mm, is 20mm in depth and an overall diameter of 64mm to the edge of the teeth

Can anyone confirm as to whether the sprocket 'B7' is one piece or two?

[Castellated nut]

The Rover sprocket is definitely duplex.

Incidentally, what's all this "mm" stuff? The only mm in my engine are in the cylinder bores and the spark-plug holes! I heartily endorse a little program available from the Washington State Department of Transportation site at http://www.wsdot.wa.gov/reference/metrics/factors.htm" target="_blank" target="_blank called "Convert.exe" which will convert virtually any unit to any other. You don't even have to install the program - just download it and double-click the file.