I'm just a simple hobbyist, so 'real' calibration is beyond my budget - the best I can hope to attain is reasonable accuracy achieved by purchasing what I perceive to be the most reliable tools combined with some common sense of the readings I get and comparing those results to any other gear I have.
Anyhoo, I just recieved my set of ST42 Tweezers and my initial impressions are excellent - these tweezers look and feel like a high quality tool. They have just enough weight in the hand so they don't feel 'cheap', yet not so much as to be unconfutable using them. The oled display is excellent - very sharp and readable. Despite the small screen size there is a lot of information and it is easily read at board distance. The Hold function works well, but that setting seems to reset every power cycle? I'm still learning the menu system, which although is easy to use does have a lot of options.
I did order the optional curved blade tips, but now that I have the tweezers in my hand I'm not sure if I really needed them. There was a note in the box indicating that the tips and a set of spare screws were inside the case. But in the excitement of receiving the package at the post office I could not resist opening the box in my car - I may have lost the screws in that process... The tips were wedged between the foam and case side, but I did not find any screws - I only see one small plastic insulator type bead... I'm not sure if I lost parts or if that insulator is needed - the tips that came attached to the tweezers do not appear to have this insulator on the screws. Not really a huge deal, but it would be nice to have a list of all the parts in the kit so I could verify everything was accounted for. A photo attached below shows the insulator bead - if anyone else knows what that is for I'd be appreciative.
The calibration board is nice - both as a learning tool and also a sanity check for readings. I haven't had a lot of time to play around with calibration, but as a first pass out of the box every component on the calibration board measured within a fraction of 1%. Again, I have nothing to validate those results at this time but they do seem reasonable.
All in all I am very happy with this purchase - while I don't do a lot of smd work these are still very helpful for boards stuffed with components and are a lot easier to use than test probes in those cases.
Edit - forgot to mention that my purchase was motivated by the desire to obtain an LCR type meter to add to my bench. I considered the DE-5000 that seems widely respected, but these tweezers looked to provide much of that functionality while also being useful for work on cramped boards. Also, I got the sense that the DE-5000 tweezers were lacking and everyone seems to be hacking togther some kind of Kelvin clips for that meter... I figured why noyt just get smart tweezers instead?
Edit 2 - In addition to a list of parts included in the package, it might be helpful to enclose any optional small parts (tips, screws, insulators?) in a small bag or similar package so they are not loose in the case. The tips aren't likely to go far, but if there were screws inside my case they are the size of a grain of rice and very easily lost...