Sheet Pile Retaining Wall - Irregular Edge O
... cast resin
2-1/4 x 8"
These started being used around 1915 and are in current use today.
The prototype is made of interlocking steel sections driven in place by a pile driver. As with many items of this type, the full size sheet pile was available in many sizes. This makes these wall usable in different scales.
These were usually painted black and rusty below and above the surface of the water.