Right - I got that. But since those don't exist on your old bridge, they couldn't have been the same. So I was theorising if you were comparing based on screw position instead.fendermcfenderface1! wrote: ↑Fri Jun 28, 2024 9:40 pmMrSparkle- by string spacing I meant the string grooves in the Mustang saddles, which are predetermined, unlike the original threaded saddles which might offer a bit of variation by picking exactly where the string lays in the thread valley. What is TPI?
TPI is Threads-Per-Inch, it's a measure of the coarseness of the thread on an imperial fastening. Metric fastenings (like the M3 posts in your Mustang bridge) are measured differently.
If you want to double check the big-bag-o-25-screws has the correct thread spacing you can measure the distance between a few threads to check, and do some basic arithmetic to work out how many threads would be in an inch!That's normal, those guitars are all built with a 9.5" radius as they're a "modern" design. 2 1/16" is 52.5mm though, not 54mm.All I'm seeing are 55 mm string spacing and 9.5" radius, my neck is a 7.25" radius.
The "correct replacement" for your guitar is the American Vintage Jaguar/Jazzmaster Bridge, not the American Professional. If you decide to go for a Mustang-style bridge with narrower spacing, the correct answer is Staytrem; or a similar aftermarket part from Halon, etc. It's not a part Fender make*.But again; I think we're getting into the weeds here. I'd try ordering those aftermarket grub screws (the pack of 25 in choose-your-length) and going from there. Go back to the original plan of just replacing the one screw, rather than getting lost in the maze of different "upgrade" bridge options. Though honestly in your place, I'd put a pair of fresh screws in and seal the lonely 60-year-old one in a baggy as "case candy". That's just me though.
List the rest of the screw bag on eBay as "individual Jaguar/Jazzmaster bridge-post-screws" for $2 each and you won't be left out of pocket.
* Correction, I forgot about the Marr bridge. I'd still go Staytrem though.
There's a couple reasons why - the Marr bridge has brass saddles, the vintage ones were originally steel, like the Staytrem. The Marr is commonly called "Fender's Staytrem Copy" but it really isn't - it has sleeved bridge posts to prevent sinking, but the Staytrem has a few other upgrades like saddles that can't move laterally, offset screws that can be adjusted easily with the strings on; and the saddles are positioned without springs which gives more adjustment room and a couple other benefits. But still; don't buy a Staytrem, buy a big bag of screws. 
