Underwelting hand tool?

[ChicagoWayVito]

So I found an old local news story video for Optimo Hats. In the video, it very quickly shows Graham using a hand tool (curling shackle?), and looks like he is putting in the underwelt with it to be stitched down later. Does anyone know of this or have any details?

You can see this very quickly in this video, starting at the 30-second mark.

Here are some images that I lifted from the video.

While I have a binding attachment for my 108w20 that will do the underwelt, it cannot put in the underwelt continuously. You have to leave a 2-inch gap and then finish it by hand.

I do have the D'Orsay curling shackle, I wonder if I inverted that hat if it would essentially put in the underwelt.

Any ideas about the tool?

@Art Fawcett, @mayserwegener, @humanshoes, @belfastboy

 

[ChicagoWayVito]

Ok, Ermatinger may have answered this on page 67 of Scientific hat finishing and renovating

So I can use the D'Orsay curl to get a "flat edge". I would love to find a hinge shackle though and add to my toolset.