Not sure I understand your question. I have seen tons of these:
But do you mean have I seen them being used? Yes, I have seen tons of them doing their job. They predated digital controls, and were very reliable. The one drawback to them is that they tend to lose the 'top end' of their range as they age. Also, people sometimes mistake the capillary tube for a ground wire and cut them.
If you mean have I seen these for sale, used, no. I do not sell them used, and they are such an important part of the safety systems of a hot tub that I try to replace them rather than adjust or repair them.
how am i doing?