Reddit mentions of Kluson SD9105MN 6 In-Line Vintage Tuning Machines, Nickel

Totally worth fixing it up. I'm guessing it's a Vintage Modified series Jaguar, which are on the nicer end of what Squier produces to begin with. As long as it isn't broken, new strings and a setup should give you a totally playable instrument. If you want to upgrade parts you have plenty of options at different price points.

First of all, this four part series of acrticles should be requiered reading for any Jaguar/Jazzmaster owner. Lots of helpful setup tips and general information in there.

tl;dr- Shim the neck and use heavier (11/12 gauge) strings, as that was what the guitar was designed for. I have 11s on my Mustang and they feel like 10s do on longer scale guitars; not unreasonably stiff. I've even been considering going heavier.

Hardware:

• Personally, I like the vintage style tuners that come stock on the VM Jags. I'd only replace them if they give you tuning trouble, and even then I'd just swap in some Klusons in the same style. I like that it doesn't leave you with sharp string ends; very clean and orderly. (How to String a Guitar with Vintage Style Tuners)
  
  
• You can swap the Squier hardware for a Fender Jaguar/Jazzmaster tremolo and a Mustang bridge. Some people have issues with strings popping off of the saddles on the stock bridge; the Mustang bridge's saddle design seems to help. If you get a Classic Player tremolo system (I think, might want to double check) it should have a screw-in collet, so the arm will mount more like a Strat. Other models use the traditional push-in arm/collet, which some people find to be too loose.
  
  
• You could get a Bigsby with a Vibramate if that's more your style. That may get a bit expensive, but I've done dumber things to cheaper guitars, so I'm not one to judge. Stetsbar would be a similar option, but I think it would require chopping off a bit of the pickguard around the bridge.
  
  
• If you don't mind spending as much as the guitar itself would go for on the used market, you can get a Mastery bridge and vibrato. I bought a set for a Jaguar I was working on at the time and it feels much better than anything else I've tried. When I sold the Jag, I kept the Mastery. I ended up selling the tremolo and stuck the bridge on my Fender Mustang and really like it; better sustain, no string binding when using the vibrato, much more stable overall. Just ludicrously expensive, unfortunately.
  
  Electronics:
  
  
• You can get a wiring kit like this one from 920D, or use it as a reference to part one out yourself, which might be a bit cheaper. You may need to modify the bracket on the upper horn and sand away some material inside the cavity to get the larger pots to fit. If I remember right, the bracket dimensions on the Squier Jags are different due to the smaller potentiometers they used.
  
  
• There are plenty of traditional options for aftermarket Jaguar pickups, as well as a few non-traditional options. All the big names in the boutique scene make a Jaguar pickup (Curtis Novak (He also does a Jag-sized Lipstick Pickup), Lindy Fralin, Jason Lollar, The Creamery (UK based and can have long lead times, but some very cool options), Porter), as do a number of less well known pickup winders. I've worked with both Buddha Pickups and Sunday Handwound Pickups and both have been great. There's also Seymour Duncan, a good solid aftermarket pickup choice for pretty much any project.
  
  Fun Stuff:
  
  
• Another pricey part, but I recently picked up this Hagström Tremar style trem from a supplier in Germany. It's weird and I love how it looks, but it's more or less the same as a normal Jaguar trem in terms of feel and functionality.
  
  
• If you want to get creative with your wiring, Faction Guitars make a bunch of different control plates for whatever your needs may be, including hardtail adapter plates if you don't want a tremolo at all. I've also found their Slider Switch Spacers to be helpful on some builds. It makes the switches less immediately accessible, but also less likely to be engaged while strumming.
  
  
• The two way slider switches can be found in black, white, and occasionally red if you want to color code them like some of the old Japanese-made department store catalog guitars did.
  
  Also, come visit us over at r/Offset. We love all guitars with offset body styles (Jaguars, Jazzmaster, Mustangs, oddball guitars from the 60s). Lots of good insight over there.
  
  Edit: Formatting and spelling mostly