One drive TU56... interesting, didn't know those
existed. I've only
seen pictures of one drive TU55s, but clearly that's not what you have
(the unit selector switch gives it away).
I have one (my only TU56). the front casting is the same as for a
dual-drive one, with the trasnport and heads fitted in the left drive
position. There;'s a metal plate with stud fixed to it placed over the
hols for the second set of motors/heads/controls with nuts and washers on
the studs inside the unit to hold the blanking plate on.
-tony