Please note that the vast majority of generic certificates were (and still are) printed by Goes Lithographic Co. in Chicago. Most show the ellipse-shaped "GOES" logo in the lower left corner of the border. Many local printers bought partially-printed Goes' certificates and then overprinted them with company names and other details. Some of those secondary printers added their own imprints as in the example below. I list most generic certificates as "Goes", because it was the primary certificate designer.

This is an example of the bottom left corner of a typical Goes' certificate. It shows both Goes' logo in its most common location. Please note that the logo sometimes appears close to middle of the bottom border. Some Goes certificates lack the logo entirely, and simply carry a notification like ©GOES. To complicate matters, there are probably around a hundred generic certificates that are identical in all respects to Goes' certificates, but they lack any attribution. Some may be "knock-offs", but I suspect most were really Goes' certificates.