16th century French made Twibill known as a "Bisaigue"

Three weeks ago I posted a tool that I bought at a vintage tool auction. I called it a "European Twibill".
I since had found more information on this rare tool. It is a French style of mortising tool, similar to an English "Twibill", but was used much earlier.
It was called a "Bisaigue" and is pronounced " Bay-say-gue' "
These tools were known to be used in the 16th century and probably earlier. They became lost in history after the 17th century and there is little record of their use after that time.
Photo # 3 shows a cartoon drawn grandfather showing his grandson a bisaigue.
Photo #4 shows a medieval wood cutting of a carpenter using a "Twibill" as a morticing tool.
I wondered why it was so much longer (42 inches) than an English Twibill (16 inches), and how was the handle held in the tool?
There appears to be no way of keeping an added wooden handle attached to the tool.
I found out that the tool was used by resting the long portion of the chisel that was not being used, on the shoulder of the carpenter while softly striking the mortice with the other end.
Using short soft strikes in this manor, allowed the user to tire less, thus doing a better job..... Also, with the tool close to the body during use, there is no need for a longer handle and the bisaigue probably never had an extension to the forged attached handle.
They are reported to be quite rare and only a few are found in European museums.