340 Steel Crank Questions

I recently sold a like new 20 plus year old still in the original box 340 Steel Crank on eBay (Item # 330181279119).

The buyer is telling me this crank has no centering ring to mount the flex wheel and the flange holes are not threaded. He also told me a machine shop in his area said this is a “Boat Crank”.

Can anyone tell me if this could be accurate and if there is such a thing as a boat crank and can it be machined for uses in and car engine?