On those stampings, I think they were post service.
I don't know what the first line is.
The second line is a chassis number issued by a registration authority.
The third line is the date of manufacture.
The last line is the aggregate trailer mass.
The canvas can be swapped between trailers.
I would assume the bar code reflect the number plate that was attached when the auctioneers got the trailer.
What are the manufacturers tub and chassis numbers?