This trailer is meant to be paired with the Diamond T Prime Mover Tractor No.15a. It is referred to as 16a Transporter Trailer and was released in 1955, it was made in tan with metal wheels until its deletion in 1960.
The reference I found for the Diamond T Prime Mover on a specialist tractor website mentions a 'Rogers' trailer being paired with the Diamond T to provide a wartime tank transporter for the British Army, which is what this appears to be. Rogers Trailers is still in business and on their history page on their website they show a picture of one of their WW2 tank recovery trailers which looks very much like it. On the site - which I could not see too well because of some errors on it, they say they built seventy of them a week during the war.
There are no rare versions of the trailer, except for the ones which retain their flick-over ramps as they are usually broken off
