Still in the instrument making family, here is my thickness dial caliper :
It has a steel frame, the profile is a T, for stiffness, it is welded.
My personal touch to this classical tool, is the brace that has the goal to yet stiffen the frame.
Generally, with this kind of tool, the widest it is, the less stiff it is, but you don't always need to measure a wide plate.
So I designed this detachable brace, fixed with two bolts.
If you are making a violin, you do no need a too much throat, so your can benefit from the stiffest configuration, which is the one shown on the picture, with the brace in the center.
If you are measuring larger plates (guitar/cello) , you can move the brace more on the right or even remove it.
Even without brace, this construction is quite stiff, if you push with the hand on the arm, you only get maybe 2 to 3 10th of mm bending.