It would have been made after the mid 70s, as it has the gold bottom trim and metallic dial, which is the last of the center dial designs, that ended in 1980.
A 606 does not light up in the back, but an 806 or 906 does, a very cool feature.
I noticed/learned offhand at my friend Roger's house that this final incarnation of center dial Maytags does not have the little orange pilot light above the dial that the earlier models do. The late 806 models do not have the chrome strip on the front of the machine or the chrome lint filter top. Lastly, this final incarnation does not have the trademark Maytag "snapping timer".