If a barrel doesn't have a twist rate on it or caliber how can you locate that info?

Caliber: measure it with calipers
Twist: put a patch on a cleaning rod and insert the whole rod from the chamber end. mark the top of the rod at the muzzle. start pulling(the rod should twist). pull the rod carefully out until the mark is on top again. measure the distance that the mark is from the muzzle. that will be the twist rate.