Sprocket 50 Roller Chain 19 teeth Taper-Lock 1610.   Martin     Made in United States.  Overstock Clearance.  I have plenty more sizes, 35,40,41,50,60,80,100,120 and types, bored to size, plain bore, taper-lock, QD, and Browning, that I am working on listing.  If you don't see the sprocket you need listed, please ask.  It may be waiting on my shelf to be listed.