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.