Yes, the answer is in my updated M14 book. There was an original intention to sell members M14s rendered semi-only by welding up the selector lock. Examples were submitted and approved. However the new rulings in the 1968 GCA act killed the project. Lots of info and photos in the book on the subject.
There were two TRW NM M14s in civilian hands. One owner called ATF who promptly confiscated the gun. He took them to court and won because the rifle was built as a semi NM M14, despite the fact that it was the same as any M14 with a only selector lock keeping it from being full auto. The court ruled that the rifle be returned to the owner and the court's ruling ONLY applied to that Rifle. It is unknown if the other one was granted the same privilege. The rifle that was allowed to be kept was sold a few years back and is still a non-NFA Title 1 rifle and still in private ownership.
There are several color pictures of the rifle and several related documents in my updated M14 book.