The originals, of course, were cream-bobbined open humbuckers, but I was never happy with the woolly and decidedly unFenderlike sound on the lower strings. I remember using it on one occasion at the Southend Club - I got a very muddy sound through the AC30 in use there. Likewise, I once played it to a couple of backing tracks at the Pipeline Convention - the amp was a bit brighter, but clarity was lacking on the low strings.
See the pics at:
http://www.flickr.com/photos/29785641@N07/
(Use the "slideshow" feature - upper right.)
The Cats Whisker "Phat Moggies" are usually produced in a cream finish, but the (UK) maker was happy to supply my order in custom-made white cases for a more traditional Fender look. He dubbed them the "White Pussies" as a result. There's now something very Jazzmasterish about the look of that cheap guitar, isn't there?

I auditioned the sound through a Vox Amplug and 'phones in order to adjust the string balance on those polepieces.
Then tried it out on Sunday at a local jam - what a difference! Clear, ringing, low notes.
Of course, it's a bit of an oddball guitar, unlike anything else, because of its unique features:
- 24" short Jaguar scale
- Stratocaster-type bridge (it too is a replacement - a steel-block Wilkinson with pop-in arm)
- Gibson-type P90 pickups (even if they do look Jazzmaster-ish).
So it isn't quite right for a Shads sound, but it sounds great for Ventures material and (with both pickups on) for the Jet Harris Diamonds and Scarlett O'Hara sound. If I can get to Dartford on Thursday, I'll bring it with me.
JN
PS: Read about the Vista Series Jagmasters at: http://en.wikipedia.org/wiki/Squier_Jagmaster