@ablaze They are portable sundials. The compass aligns with north and then the gnomon gives an indication of sidereal time. These might be 16th century. Ivory face. A huge collection in the Pezzoli Museum in Milan.
@ablaze They are portable sundials. The compass aligns with north and then the gnomon gives an indication of sidereal time. These might be 16th century. Ivory face. A huge collection in the Pezzoli Museum in Milan.