„This machine was provided with a large hollow tubular needle bar, unlike all the other machines which were furnisched with a thin solid needle bar.
The three-thread cord was made with a thick soft wool or some such substance which was inserted from top to bottom through the needle bar. The machine was set up as for the two thread cording on the K machine and this thread wound itself around the wool and the chain stitch, making a very thick, rich, raised, twisted cord. The machine could also make a chain and moss stitch and could be set to do a stitch that was called a picot or spark or claw stitch (plate 51) and could also do gimp work. The soft wool that was inserted down the needle bar was counted as the third thread.“
(Quote from Machine Embroidery a complete guide by Christine Risley)