Mark posted this model in the AX topic, as he had identified a drawing of it which was labelled (AX). However, the Naval markings are a clue that this model represents a design from the 1968 RINAA (Research Investigations Into Naval Attack Aircraft) I study.
Mark's VMX PDF has a section on Vought's past naval studies which clearly labels this design as a RINAA I study. No doubt the same basic design was considered for AX as well.