They were marketed in the U.S. as the PT 280 MP & OS, and in Europe at the PT 630 and 690.
I have a PT 690 whose feel is exquisite. It is like a lower-powered, even more comfortable Bumblebee (original Agassi Trisys 260 OS). Unfortunately it, like many 1990's Head graphite/Twaron composites with 660 or 690 head size, was distorted on some stringer long ago.
El Zed, does yours have its original hoop shape?
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1. Never tell anyone everything you know.