Need Help Identifying this Part

[Robz51]

I've had this part in my garage for years and would like to know what it is. I recently cleaned it up to get a better idea of what I have. My guess is it's a crankshaft mounted fan mount/pulley. Maybe a 39 or 40 flathead but not really sure? Any help would be greatly appreciated. I've never posted a picture before so I hope this works. Thanks.
Rob Jones

 

[rotorwrench]

Looks like a crank pulley for a 39 deluxe Ford through 1941. The types that had the crankshaft mounted fan.

 

[Bruce Lancaster]

Second vote, rotor is 100%

Secret information I found recently in an olde speed magazine: When that pulley is used to drive a 4-71 GMC blower, it will fail once boost goes beyond 5 pounds!

 

[Robz51]

Thanks guys! I have no idea how I came across this part since we've only had 8BAs in our Fords but once you amass flathead parts you tend to forget where and when you got them.
Rob Jones