I'm thinking good benchmark machines might be
either the PDP-1 or IBM 1130
as they bridge the gap in my mind between mainframes and "personal
computers".
Being primarily a DEC collector, I would choose the PDP-1 out of these two,
but one of the CDC line, such as the 6600, might be of interest as well, even
though it is not much of a "bridge"...
--tom