How would you know if a frame is a Pinarello Gavia or a Montello ? I can only say it's stamped 88 on the BB, (in addition to TREVISO...) so that should be the year. And both had no bridge on the chainstays...
Seatstay caps? I'm not an expert but Montello would have the GPT panto and the Gavia has a different seat stay cap with PINARELLO panto'd rather than the GPT