Photo © Israel Museum, Jerusalem, by Ofrit Rozenberg Ben-Menachem
Walnut wood, carved
Inscribed in Hebrew with the initials of the sentence “to rise in the morning in service to the creator” [Shulhan Arukh, Orhot Haim, Laws of Rising in the Morning 1:1]
L: 39.5; W: 7.7 cm
Israel Museum; The Feuchtwanger Collection, purchased and donated by Baruch and Ruth Rappaport, Geneva
Accession number: HF 0171 ; 199/032
Many, but not all, shul knocker's hammers were shaped like a shofar as it had the same mission -- to wake people for prayer.
For more info, see http://www.jewishencyclopedia.com/articles/13326-schulklopfer.