According to Albert's book that is a Deleware State Seal button. Here is the complete text of the button description:
DL 7B. The cow faces left. "Superior Quality". RV 1
note; Reference should be made to the American Rifles, a military company instituted at Wilmington in 1875. This company represented Deleware in the Centennial Legion in the great military parade held at Philadelphia July 4, 1876. No record is known that a button other than the staff state seal button was worn.( For details, see National BUTTON BULLETIN October 1945 also January andJuly 1946)
I don't understand what all that means. But, I think it means the button was worn in that parade only. I could be wrong because the RV(relative value) is 1 and that is the lowest value they give.
I sent you a personal message.