This is a representation of the coat of arms of the Roman Catholic Diocese of Harrisburg.
Argent on a cross Gules a shamrock of the field on a chief Sable a crescent Argent between two plates.
The following Commons images were used to create this image:

 File:Roman Catholic Diocese of Erie.svg by Niagara (talk · contribs) (mitre)
 File:Old French Escutcheon.svg by Masur (talk · contribs)
 File:Croissant Héraldique.svg by Odejea (talk · contribs)
 File:Shamrock of Ireland (Heraldry).svg by Sodacan (talk · contribs)
Own work
Alekjds