Thanks gang!
Nancy, it does! "Pat. Sep 87"...I'm pretty sure that is NOT when it or the machine were made, but I really don't KNOW when the machine was made..I'm hoping to find out tho!
Edited to add:
A bit of detective work with my partner, Google, tells me that this machine was made in the early 1900's... I found this "timeline":
In the early 1900s, the company apparently moved its operation to Cleveland, Ohio, and was renamed the A.G. Mason Sewing Machine Company. In 1916, the company was purchased by the Domestic Sewing Machine Company which itself later merged with the White SM Co. in the 1920s.
So because the slide plate tells me that the machine is A.G. Mason, Cleveland, OH, the machine was made after 1900, but before 1916....