I'll always grab an old sea moss pressing when I find one, but this one I like for the back of the card as well as the front. Marking the month of August 1917 (the calendar bit was cut and pasted onto the card) I presume it was the maker of the pressing who wrote a few notes to herself on the reverse, beginning with "Avoid low spirits during dog days by looking into Jesus." ! Also note - "Sun stroke from prosperity may be avoided by sitting under Christ's shadow." So, not quite your usual sea moss sample!
4 1/8" x 5 3/8". Very good condition, sea moss is in perfectly preserved condition.