Singer did not produce these buttonhole workers, but depicted them in their books of how to use their attachments. I have the 1924 edition of Machine Sewing and pages of instructions are given by Singer of how to attach, adjust, and make buttonholes with this attachment.
During this time, Singer had not yet manufactured a buttonholer. My quest is to find the date they first produced them. Any readers with that information - please share! share! share!