If yours has the ornate decals like leon posted, then it's an earlier model. Sears sold this name with both rotary (round bobbin) and vibrating (shuttle).
I believe most of them were made by National, so I'd guess that puts them to a date after Sears stopped using Davis (early 1920's).
I have a Damascus Grant (rotary) manual that shows this model
and it also includes this "updated" insert for the latter design.
