I have two of these. Mitutoyo has a very strong reputation among professional machinists for accuracy and durability. This caliper is in an entirely different league from the more common copies that sell for a fraction of the price, several of which I've also had. It's worth every extra penny that you'll pay for it.
Digital calipers are under $10 on Amazon (but reliability may be "iffy"), or $20 for a much better one at Harbor Freight. The HF is a copy of the Mitutoyo Absolute Digimatic ($125). Very handy tools for a lot of things. Examples; nut width, string spacing, fret height and measuring the thickness of old credit cards to be used as gap gauges.
My 'toyo has well over a decade of shop use and still works great.
I guess that the OP is commercial spam - don’t click on the link - but the topic has some interest. I have old micrometers and vernier callipers that do the job well enough, similar old tools can be had for very little of off eBay. Save your money, give an old tool a new home and don’t waste resources by unnecessarily buying new.
Honest to goodness, I think almost the next purchase after a basic toolkit and a level, for many people, ought to be a quality 6" caliper and a 0-1 micrometer, along with a diameter tape. I struggled along without good measurement tools for decades, but any task involving more than the very most basic measurement has become orders of magnitude easier once I purchased these basic tools for myself (I've been using precision measurement instruments professionally for 40+ years).
Once you have a measuring tool, you will understand that everything must be measured! (do you know how wide your thumb is?)
But seriously, I have measured the strings on my uke to help find out why the intonation is forked up on this little guy! Lots of comments on UU that new strings fixed the problem, so I'm writing down the diameters to see if that informs me that thicker/thinner strings help or hurt.
Or when I've bought a used ook then want to replicate the same gauge on the new set.
- It feels too tight, I'll try a slightly thinner string of the same type.
- It's too loose, I look for a slightly thicker gauge of the same type.
- When one string is not in tonal balance (loudness or timbre*) with the other three.
Where it gets tricky is when you go from a wound to an unwound, or vice versa. Then, it's handy to know the diameter of the opposite so you can find one that "comes close" to measure so a choice can be adjusted up or down to reach the desired tension and pitch. Experiment.
* In music, timbre, also known as tone color or tone quality, is the perceived sound quality of a musical note.
... Also, it's good to know the diameter for predicting if it will fit in the nut slot.