you are probably talking about the "Guild frequency tested" chrome covered (early ones have a white top) single coil pickup found on S-50 Jetstars and S-100 Polaras from the mid-60s. they also appeared in some hollow/semi hollows like the X-50 you reference, and others. The pickups sound incredible to me in my Jetstars, and in prior threads it has been discussed that to have those pickups in a hollow Guild would certainly be a "winning combonation." some have reported they have "lower output" than other pickups, but I have not found that to be the case with the (3) guitars ive had experience playing that had them. Those guitars are all single pickup guitars, so a double pickup guitar may have been wired differently, or something?? they sound mighty good, to my ears.
While I cant comment on a Franz or older generation of X-50 per say, I will say the "frequency tested" pickups do sound to me a bit like P-90s ive had experience with (newer Gibson LP Jr/melody maker...). Also I would think the general overall condition of the guitar and playwear (neck angle, frets, finish, past repairs, condition of the wood, etc) would have a much bigger imact on value than the pickup, especially if it is the original pickup, but that is just me. If you are specifically looking for a Franz, this is not it. if you are looking for a nice X-50 with any original single coil pickup, any of them should work. the "frequency tested" and "micky mouse" pickups have *not* been widely reported as "pickups to avoid."
The value of a Franz-equipped early 60s X-50 should not be so different than a Guild-equipped mid-60s X-50. if it is, than maybe the Franz is more sought after/less of them? or just the older vintage? Anything from Hoboken should be pure gold.
