Does it look like this?
?http://archive.computerhistory.org/resources/still-image/DEC/PDP-8-S/dec_pdp-8-s.display_of_pdp8s.102630596.lg.jpg
That is supposed to be an 8/s. Could it be that the first(prototype?)
8/s where put in an Straigh-8 chassi?
The front panel does look just like that, but the upper
part of the machine in the manual is the usual smoked
plexiglass. ?But I could certainly believe that when it
came time to prototype the 8s, they recycled prototypes
of the straight-8.
BLS