Optima Mid LWB chassis question (picture!)

[j0pp3]

I found this chassis lurking in my pile of optima parts. I can't seem to find good source of what optima mid model it came with or if it was some kind of after market chassis.

First I thought it belonged to the Optima Mid Custom Special but when image googling that model I get confused.

I know it's not from Turbo Optima Mid Special as that model have a carbon fiber chassis. And definitely not from Optima Mid Custom as that model have a brownish alloy chassis.

Here is my chassis in question. It's in pretty good shape...