Well this is embarrassing. Once upon a time, I wrote about the Lockheed P-80A carrier trial aboard FDR with this illustration.
I posted the page here along with additional information and photographs: http://tailspintopics.blogspot.com/2011/11/lockheed-p-80a-carrier-trials.html
Yesterday, while providing information to a friend who was writing a book on Landing Signal Officers, I had the opportunity to review the picture I used to establish the presence of the barrier guard in front of the windscreen:
This is another from the same event:
Not proof, but it is not present in any of the other pictures taken of this airplane during shore-based testing.
I had concluded that it was a barrier guard (or strictly speaking, a Davis barrier* activator) necessary in the event of a collapsed nose gear) because I was expecting to see one. A scabbed-on guard had been added to the McDonnell FH-1 for its carrier trials accomplished three months earlier and was standard equipment on Navy carrier-based jets until the advent of the angled deck.
My guess is that the P-80 trials were accomplished without a barrier activator by the simple expedient of keeping the deck clear, sort of an early version of the angled deck. But, see Gerald Asher's comment below.
*For a gouge on the difference between the standard barrier, the Davis barrier, and the barricade, see http://thanlont.blogspot.com/2010/10/barriers-and-barricades-one-more-time.html