You have the chassis of a rear mounting dump trailer see photo below of mine. The brake is very crude and not much more than a parking brake with the metal pad rubbing on the tyre, it is applied by pressing heel down on the bar, it then locks under the mechanism on the post which is missing from yours. If it is not raining tomorrow I will get some more photos and dimensions of the missing post etc. The tipping body is the same as the front mounting barrow, see extract from sales leaflet below.
Attachments:

