I hear stories of people selling rigs, and telling the buyer that all the stuff is from Marlin Crawler, only to find out it isn't. I've heard of guys buying axles with the PO selling them as having Longfields in them, and they were stock shafts.
If Dcal714 would take better pictures of the adapter, we could tell the manufacturer of the adapter. There are two companies that makes nearly identical adapters, and from the outside, the only way to tell, is to see the stampings.