Jazzmaster Jaguar vintage style tremolo chrome with Tremolo pin lock

Jazzmaster Jaguar vintage style tremolo chrome with a unique "trem Lock" function.

String spacing = 50mm.
Mounting screws and tremolo arm are included.

How does a trem lock work?
The most interesting feature may be the unassuming little button on the forward edge, known as the trem-lock.
Many players erroneously believe that engaging this button effectively hard-tails the vibrato, but that's not at all correct.
In fact, with it engaged, you can still depress the bar—you just can't pull up. And there's a good reason for that.
The actual intended purpose of the trem-lock button is as a sort of mechanical memory for when a string breaks.
When a break occurs, the decreased string tension causes the unit to pull sharp.
Sliding that button back, the vibrato "recalls" the tension of the remaining strings, returning them to pitch automatically.
It's all about balance.
To get the trem-lock working properly, make sure your strings are tuned, then depress the vibrato arm until you can slide the button all the way back.
If you release the arm and the pitch is lower than it should be, you'll need to loosen the spring tension by turning the screw counterclockwise.
Return your strings to pitch, and repeat until you've achieved balance.
If you can easily slide the trem-lock button all the way back but still pull up on the bar, then you'll need to tighten the spring's tension by turning the screw clockwise.
Incidentally, setting up the trem-lock button is also useful as a guide for the overall feel and play of the vibrato.
In my view, doing so brings out the best in the system, with plenty of upward and downward pitch variation.
Of course, I recommend that players adjust their instruments according to their needs, so if what you want is maximum downward travel, then, by all means, tighten that spring.

Below picture shows the tremolo unlocked:

Below picture shows the trem lock in function: