I've purchased two sets of these (
Universal Polymer TV / RV Computer Monitor Bracket --2 piece set--(BLACK) | eBay). Installed the "female" brackets on the metal swing-arm interior TV brackets in both the front entertainment center as well as the metal wall bracket in the bedroom. Installed the "male" brackets on the backs of the two TV's. I can lift either TV up & off the wall brackets for traveling, or take either one outside & hang it on the matching "female" bracket mounted on the side of the TT. All the exterior mounts I've seen are the same heavy duty polymer. Never seen a metal exterior bracket.