IIRC Snap On tool dealers have a torque wrench testing rig on their trucks or at least used to. If you can contact one he can probably check a torque wrench for a nominal fee.

Click type torque wrenches can easily go out of calibration, sometimes drastically. My brother had a Craftsman one do so years ago so he switched to using beam type torque wrenches. Beam type ones of decent quality are a lot more rugged as are good dial types.