This is a uniform nicknamed "OTAN" (NATO) because it coincided with Spain joining NATO in 1982. I think the OTAN uniform came into use around 1984, but not entirely sure. The velcro shows this to be a later production when they replaced the buttons with velcro (which soldiers did on their own too). It's a fairly washed out example which I initially took for the browner M68 "Garbanzo" uniform.
The stitch marks over the right breast pocket must have been for para wings. Flags were worn on both shoulders and probably rank/name was worn over the left breast pocket. The Spanish messed around A LOT with different rank/name configurations so it's hard to tell for sure.