The original Trails has plastic housings and when the got hot the zero wandered. The housings were changed to magnesium which solved the issue. The later Trails were some of the best thermal scopes made.

To find real resolution of IR (or NV) scope, if not given in specs. Take FOV in base mag, convert to inches and divide by the detector element, i.e. 380,640, etc. Multiply by 2 (it's an optical thing). Closest you can get POA & POI.