George, you are a wealth of knowledge.For what it's worth ..
The soft-top frame pictured is from a 1959 or later Giulietta Spider as it features the flat steel folding arms that are joined with flush rivets rather than the special flat-headed screws that were used in earlier frames.
It also includes a tab on the forward-most arms that positions the canvas flap at the side window.
This frame can be fitted to all 101 chassis, and with modification, 750 Spiders.
When erected with the correct canvas, it forms a roof-line with a lower profile than earlier soft-tops but not as smooth as a later Giulia top.