Many of my acoustic guitars came with pickups installed. Since I never use pickups, I've yanked out virtually every one, so I'm pretty familiar with the various species.
Pretty sure that's an early one-piece pickup jack that -- unlike most -- DOESN'T screw in. Rather it is squeezed (or possibly hammered) in, the way some tuner ferrule bushings are.
Like those ferrules, the jack has grooves in the barrel which lock it in place and prevent it from turning. (So don't try to unscrew it!)
First check inside with a mirror to see if there is a nut and washer securing it. (I don't think there is.)
If not, you just have to pull it out -- which can be confoundingly difficult. Since I never cared about the pickups enough to try to salvage them, I snip the wires leading to the jack before tyring to pull it out. If that seems too drastic, you can always heat the soldering points with a soldering iron in order to remove the wires after the jack is partially out.
As I say, it's a tough job getting the damn thing out, and risky using anything as a lever to extract it (like a clawhammer) without damaging the jack and possibly the guitar(!), so if you have resort to that method, pad the guitar (and the jack if you care about it) and apply pressure slowly rather than wrenching it.
I know -- it seems like there's got to be an easier way, but having removed several of these type jacks, I haven t found one. Brute force seems to be the only thing that works.
Good luck!
