Here are some fuzzy photos of the portacatena system on an unmolested, apparently all original, low mileage Gios (bought from Harry Schwartzman), a fine bike.
The Gios is an earlier style frame with chrome forks, "GT" in the crown and "GT" cut out in the BB. All the dated parts are 1974 and all the other parts are consistent with 1974, except the portacatena, and of course the rear dropout, which are supposed to be from 1977 to the early 80s. The two holes provided in the dropout are threaded. Later frames sometimes have these dropouts with blank areas for then holes but no holes.
Paul Arbez
Vancouver, B.C.
Canada