Most numbers are stamped on A frame although on early trailers it could be anywhere or not stamped at all. It may have been painted over also. Someone with knowledge of your TT will be along soon. If you can't find it you can always stamp it on the frame yourself from the
title number listed. There have been a few members that have had the same problem of not finding the
VIN and stamped the #s from the
title and had no hassles at the DMV.