The one I got for my Jaguar came from the Bargain bin at Guitar Center in 05', I just got lucky, bought a 97' CIJ Jaguar, and needed a bar, and this one just turned up in the bin a week later.
The Japanese Fender Jaguars use a non-lipped bar, IE, the bar has no grooves in it. The grooves you see are probably just wear marks from the bar being installed in another guitar. The lipped bars are for the old 62' Reissue AVRI Jaguars and Jazzmasters, some of the CP Jaguars and Jazzmasters used Screw-In Bars.
How it works is when you push the bar in, 4 little teeth on the "collet" use friction to hold the bar in, it's not unusual for these teeth to wear out or stop holding tightly enough. In order to alleviate this problem, you can put a slight bend in the bar (very slight) where the bar goes into the hole in the tremolo. That's what I did to my CIJ jaguar and home built Jazzmaster (which has a CIJ non-branded Trem on it). Both of their bars stay in one place, and both take a little bit of force to pull out (but not much).
You can also swap out the Collet assembly with a different one from an AVRI, or a screw-in from a CP, and I think STayTrem has a collect screw-in assembly with a setscrew or something like it.
