Few things to check on the Ballester. Matching inventory numbers on the barrel, top of slide and frame if it has them. The actual serial is on the side of what would be the MSH on a 1911 and usually on the bottom of the slide and barrel. Nonmatching not worth a lot beyond a shooter.
Roll marked Ejercito, Marina, Armada, Gendarmeria (and a few others) fairly common and worth the least. Aeronautica, CFS, Provincia de (Juan or Eva) Peron (and a few others) rarer and worth more, sometimes lots more.
Original finish a soft blue; black or baked on not original. Grip wear should match finish wear. Refinish, new grips and import stamp hurt the value. Matching original magazine helps the value.