Xetec FX-500 question

[OldComputerGuy]

On the hardware page it says the Xetec expansion is supposed to be for dual 3" drives but I have one and it has a single 5 1/4" (untested to check for density). Was there more than one variant of this expansion chassis made? It doesn't look like mine has been hacked up to use for this purpose so I can only assume it came that way when it was new.