The post diameter is consistent with Tullio tubing, a lightweight hi-tensile steel that was proprietary to Rizzato, though it has also surfaced on at least one Viner.

While I don't have any literature for the early 1980s Atala models, the two leading candidates would be Grand Prix and Corsa variants. Tullio tubesets with Valentino derailleurs were used on the 1970s Grand Prix models, with the early 1970 Grand Prix being replaced by the Grand Prix II in 1975. In the late 1980s, the Tullio tubeset was used on the Corsa frames.