Looks like a Marine NOGS bird (Night Obsevation and Gunship ). No M60s in the sponsons, FLIR unit under the nose, 20mm cannon under the fuselage, locked forward. They were quite a bit lighter than a regular OV-10A with hard points and a full bag of ordnance.
We had two of them come over and work with us for testing. The FLIR device could rotate 360 degrees, and was aimed by a guy in the back seat who had a control stick and a TV screen. Wherever he put the crosshairs, the 3-barreled 20mm would point. It was supposed to orbit the target and mark with HE rounds. The problems was, after marking a target with 20mm, there usually wasn't much target left.
A stripped and unloaded OV-10 could easily land and deck launch off a CVN. Couldn't do it with a full load, though.