This tintype photo of an unidentified father, son and two daughters shows them wearing what seems to be turn-of-the-century bathing costumes. I'm assuming this photo was taken at a boardwalk somewhere.
Tintypes were in usage between 1850's - 1930, most popular during the Civil War when soldiers visited the itinerant photographers who followed the troops. The soldiers could send these photos home in the mail without worry of damage. Tintypes weren't actually made of tin but were thin sheets of iron; they most likely got their name because the photographers used tin shears to cut the multiple photos on the sheet.
Between 1875 and 1930 photographer began taking their equipment anywhere people gathered such as carnivals, boardwalks, etc. Some permanent locations were established in places such as Asbury Park and Atlantic City, NJ and had painted backgrounds that suggested the locale.