Another interesting difference between the 128h in the L112 and those in the L150A (beyond a completely different texture of the white Aquaplas) is that the gasket which goes over the surround is different. The L112 has that gasket in four pieces separated by a straight cut joint midway in the quarter-section between the mounting holes. Those from the L150A (both 128H and PR300) is split into four pieces but AT the mounting-bolt holes.

I have no way of determining the age of any of these beyond knowing I purchased the L112s in 1982 and we know the L150A came out after the L112 and first hit the JBL catalog in 1981.