It is plastic [PE- I think] which is welded together, relative light , non-corrosive and very strong
The company that did it [I made a wooden moke -up] normaly makes all sorts of buckets [large] for argiculty use. besides that they do a lot of special stuff [gas tanks for boats etc]

the pieces are a bit over dimensioned but they work well

[see attachment]

I'm putting the tramp togeheter this week and hope to be sailing next week