Oh No! A 10 tooth Skip-tooth New Departure sprocket...

[Boris]

I found one like the one Rivnut posted. Sending you a PM.

 

[JCGarrison]

Thanks to Boris for supplying a 1/2 pitch 20-tooth ND cog and driver! The replacement went fine and I took the bike for a ride yesterday. I guess it's been about 8 or 10 years since I rode the old bike. Fast and light it is not!