This pair (actually a trio, with AC 10656) of interesting little tank cars were acquired secondhand from Canadian National, likely somewhere around 1990(?). These cars store potable water to supply accommodation cars in work trains.
Lending to the unique appearance of these cars is the coating of spray-foam insulation on the body of the tank and small heater to prevent the tanks from freezing in the winter and that huge vent(?) fashioned from an old caboose smokejack.
Both photos courtesy of Blair Smith.