Good Stuff!! It sounds like perhaps the original owner took the screw out thinking that this was necessary to disassemble the gun for cleaning. Then, apparently he lost track of the screw.
Judging only from the paint splatter and the duct tape, I'd say the Fox B has weathered a difficult period and is now in the hands of someone capable of properly caring for it.
My experience with my Fox B has, at times, been frustrating. The gun is nothing, if not an enigma.
On the plus side, the barrels are as well regulated as any I've seen. The fixed chokes (F/M on mine) throw excellent patterns. The wood and metal finishes either lead a charmed life, or they're somehow more durable than most. I seldom miss anything I shoot at with this gun. Also, I don't protect it or baby it in any way, yet it never picks up any of the tiny nicks and small scratches that eventually age the finish.
The internal design of the receiver is it's Achilles' heel. For example, there's a drift pin that sits horizontally across the bottom of the receiver (Part #27, I believe, in the blowup diagram provided by planemaker). This pin isn't knurled, spurred, or chamfered in any way. It appears the designer expected friction and inertia to be sufficient to keep it in place. If/when the pin migrates out of it's channel, it obstructs and prevents the sears from lifting. Needless to say, this can (did) cause much frustration when it occurs while a veritable flock of sharptail are coming up all around you.
It's not obvious from the diagram, but part #13 is inverted when installed. It's the screw that holds the top lever in place. Another design brain fart. I'd love to give the designer my opinion of the brilliance displayed by having a threaded screw, with no means of securing it in place, inserted upside down into a part that is moved back and forth constantly. It's only a matter of time before the stupid thing works loose and another shot is lost because a screw is obstructing the hammer!!
Before I leave you with the impression that this is a horrible gun, I should admit that there are much worse. I suppose proof of this lies in the fact that I still have mine. Lock-tite is probably all that is needed to make one trouble-free for decades.
No matter how you look at it, it's an excellent choice for a project gun. I'm looking forward to your pictures and stories as you restore and enjoy this gun.
