Model of Lockheed Alpha Jet proposal for the United States Navy VTXTS competition found one eBay.
Here is a Lockheed Proposal Model to the US Navy for a carrier based trainer based on the Dassault / Dornier Alpha Jet. Very unusual, and definitely an in-house model. The US Navy started the VTXTS advanced trainer program in 1978. I'm making my best guess that this was done and used in presentations around that time or by 1981 at the latest.