DC isn't the best indicator of output. 2k turns of wire I doubt made a huge difference in output - some pickups have that much difference just between the 2 bobbins. Most likely it tilted the EQ. Best hope is that the extra winds tilted the peak lower, away from the famous 'ice-pick' people complain about. (Or maybe higher to give it more airy top end?) FreeFrog could probably calculate what the difference might be. But you'd just have to try it to know what it actually sounds like and what it's relative output really is.
And pickups, made of metal plates, metal wire, polypropylene bobbins and metal alloy magnets, don't 'age' in any way that would make a difference in just 10 years. Especially if it spent some/most of that time in the box.
If it were me, I'd start with it in a bright guitar, like a basswood body type with maple neck, some kind of shredder maybe, or an ash Tele with maple neck (if it is one that takes a humbucker), just to see what it sounds like. You could start with a 250k vol/tone, since a JB was designed for that. 500k might let you hear more what the pickup has to offer.