recoil or stroke length measurement
Sorry but no, we had such at the foreign materiel exploitation unit in APG, MD when we weren't borrowing them from various COMs there, and I left there some years ago. Basically you have a meterstick set out of the way to witness mechanical function, clamps to hold in place. It would be filmed but you had mechanical witness ability too, like on a cannon that has a recoil witness (small collar piece shoved back when fired) that lets you know when your recoil hydraulic fluid is low.