The flange on the front actually measures 11-5/8", and the wheel is 10" across the back.  This gear is 4-1/4" high, and the shaft hole is 1-1/2" wide.  It has a great look, and a wonderful rusty patina, though it needs a good cleaning to get rid of traces of grease.  It weighs a hefty 17 lbs.

Could make a great base for a lamp or art piece, or whatever creative idea you have.

Thanks for looking!