Hitchhiker Trailer Question

[erebus]

Anyone with a Hitchhiker know where they hid the VIN on these old trailers?

There's a sticker on the left side of mine that has all the specs (GVWR, tire size, axle load, model number and name etc. etc.), but only a six digit serial number where I would have assumed a VIN would be.
Trailer is a 1983 so well after the DOT started issuing VIN's.