2.75". Image area does not have any dot screen so this is apparently a photo of a painting and left side edge reads "Copyright By J.B. Oglozinski." The scene of the three men is captioned "Pulaski - Washington - Kosciuszko." While the piece displays cleanly on the closest inspection or with a glass there are tiny black dots under the celluloid and over the entire image area, but again so tiny as to be nearly microscopic and seemingly as made. Still a most impressive piece and one of the few Washington mirrors.