The button looks like an early 1900's period button. The button shown in Alberts book would date the same with the HORSTMANN PHILADELPHIA backmark as that particular Horstmann marks dates and 1890's to 1940's A civil war period Superior Quality mark would not be stamped so well plus the shank would be different. Does the button look like it might have had brown enamel on the face? If so that would date it around WWI or so.