John, we are talking about the OP's crank, right and it's origin?
If you'll look at Mikes pictures of the FT cranks, you'll see that there is no way that the OP crank could have been made from a FT crank. It doesn't have the markings or crank flange of the OP's and I don't think they would have welded up the radius on the counter weights. Plus the FT cranks are light and use external balance. Lastly, as someone else inferred, the crank bolt would be larger.