It is interesting that these collet style seat-post binders were around so early. Great reference materials above. Hawthorne with their version in 1937(I believe one year) that accepted only a 5/8" post came and went quickly and perhaps the last bike using one? It may have been abandoned over time because of higher costs? It seems the better mousetrap than a pinch bolt through a slotted seat tube as it was much stronger and eliminated the structural forces delivered by a rider loading this area/junction of the frame. What is the OD of your collet
@GiovanniLiCalsi ??