Joe Bender-Zanoni wrote: "Is it possible that no one wants to venture an opinion?"
Joe, I did a lot of research when I found a Ross Signature at the local thrift store. Quality bike with a full set of early Shimano 105 "golden arrow" components and Ishawata triple butted tubing. It turned out to be Taiwan-made, 1983. It differs from yours (I see you bought it) in that it had braze-ons everywhere. It was also engraved Ross on the seat stay caps. In fact, everything from the tires to the toe straps to the seat were brand labeled Ross. I ended up parting mine out and selling most everything as it was too large for me.
If yours is Taiwanese, it's both earlier and one step better than mine, though the 600 gruppo is about the same vintage as the A105 "Arrow". Don't give up without a fight! If you want photos, contact me off list.
Regards,
John Wilson
Greensburg, PA