Your Fox 3” guns were mostly H and HE grade and Sterlingworth Waterfowl models. Both bring a premium price due to rarity. I picked up a AYA 12 model 3 for under a grand in like new condition for waterfowl. It came Full and Full so needs chokes opened up is steel shot is used. But it is a modern gun and built long after the concerns about internal parts being soft that many Spanish guns suffered from in the 70’s.