The Jack JK-8560G WZ-PL (1/8): Direct Drive, 3 Needle Chainstitch with Rear Puller and Flat Felled Attachment.
Probably less common now than 100 years ago when a lot of clothing, especially jeans were made with chainstitch machines. In addition to a timeless look, chainstitch seams serve a functional purpose in providing more stretch over lockstitch machines.
This 3 needle chainstitch can be used as a double needle (1/4) or single needle simply by removing the thread and needle. @ Charlotte, North Carolina