Good deal on that flywheel - it was on there! Did you see residue from any potential locking compound like you suspected?
I'd be curious to know the weight on that one. Also, the difference in finish/treatment of the two flywheels is very interesting. Given the appearance and markings on the one you have, I'm curious if it's aftermarket or off something else originally. All of the used flywheels I've seen online look more like mine.