I've seen a couple of these over the years sporting Strathearn labels, and I bought one recently (sans label), but I can't seem to find out very much about them.
This example is a mottled green with predominantly blue chips scattered about the lower half, 270mm x 110mm (~10.5" x 4.25") without fittings, and finished to the base with quite rough grinding to level it out.
Other ones have turned up in this green with darker green chips, and in a light blue with dark blue chips. Presumably to be found in other combinations.