I have this rudder for many years,  got from a yard sale in Rhode Island,  its marked  Silverton Marine,   NJ,   - its' all bronze ,   the shaft is  17" long x  1-3/16" diameter with a key slot groove that is about .165-.180" wide - not exact.   the total lenght is  35-1/2"    there are numbers and letters on item face   -  this is the best I can make out    S, 30, 31, 38, 34  BJ,  ????,    the item weighs about 32 lbs