A
Antares 531
I think this is right, and the addition of the T was to indicate thatI never heard of a 709T but if I remember right, there was a 709 (but
it was before my time). As a general rule, machines with three-digit
numbers were vacuum tube machines, and those with four-digit numbers
had transistors instead of tubes.
this 709 had transistors, not vacuum tubes. Then, if my memory is not
too foggy, the pronunciation 709T morphed into 7090, and to eliminate
the confusion the T suffix was dropped. Gordon