This is a sleeve decoration, in place. (The not-yet-attached lining is just hanging inside)
This model, like every "new" one, has caused several procedure reflections. For the velvet gowns one problen was to attach the (flat) silk to the velvet. Here it was the opposite: how to attach the velvet to the (flat) worsted. The pile of the velvet tended to make the worsted pucker.
One can go any lengths towards perfection, but for several reasons there have to be compromizes – time is limited, and time is also money.
After some (false) starts I had found a "good enough" way to attach the velvet facings. (The cording helped, too)
Now, to attach the sleeve decorations was another thing... but I think I have found a way.