A container assembly, comprising: a barrier (106, 406, 1004, 1108, 1902, 2102) defining a slot (306, 720) and further defining a window (302, 422, 1904, 2104) that opens to the slot (306, 720); a frame, wherein the barrier (106, 406, 1004, 1108, 1902, 2102) is movably attached to the frame such that the barrier (106, 406, 1004, 1108, 1902, 2102) moves between a first position and a second position; an indicator (200, 412, 1008, 1908, 200A, 200B) slidably positioned within the slot (306, 720); and a retainer (308, 1010) attached to the frame, wherein: the retainer (308, 1010) is configured to maintain the indicator (200, 412, 1008, 1908, 200A, 200B) in a first state within the slot (306, 720) when the barrier (106, 406, 1004, 1108, 1902, 2102) is in the first position; the retainer (308, 1010) is further configured to release the indicator (200, 412, 1008, 1908, 200A, 200B) into a second state] when the indicator (200, 412, 1008, 1908, 200A, 200B) is in the first state and the barrier (106, 406, 1004, 1108, 1902, 2102) moves from the first position toward the second position, wherein the indicator, when released by the retainer, moves, travels, rolls, drops, pivots, or otherwise traverses through the slot to the window under the influence of gravity; and the second state indicates the barrier (106, 406, 1004, 1108, 1902, 2102) has moved from the first position toward the second position, wherein the indicator is resettable by an operator from the second state to the first state by moving the indicator from the second state to the first state. a barrier (106, 406, 1004, 1108, 1902, 2102) defining a slot (306, 720) and further defining a window (302, 422, 1904, 2104) that opens to the slot (306, 720); a frame, wherein the barrier (106, 406, 1004, 1108, 1902, 2102) is movably attached to the frame such that the barrier (106, 406, 1004, 1108, 1902, 2102) moves between a first position and a second position; an indicator (200, 412, 1008, 1908, 200A, 200B) slidably positioned within the slot (306, 720); and a retainer (308, 1010) attached to the frame, wherein: the retainer (308, 1010) is configured to maintain the indicator (200, 412, 1008, 1908, 200A, 200B) in a first state within the slot (306, 720) when the barrier (106, 406, 1004, 1108, 1902, 2102) is in the first position; the retainer (308, 1010) is further configured to release the indicator (200, 412, 1008, 1908, 200A, 200B) into a second state] when the indicator (200, 412, 1008, 1908, 200A, 200B) is in the first state and the barrier (106, 406, 1004, 1108, 1902, 2102) moves from the first position toward the second position, wherein the indicator, when released by the retainer, moves, travels, rolls, drops, pivots, or otherwise traverses through the slot to the window under the influence of gravity; and the second state indicates the barrier (106, 406, 1004, 1108, 1902, 2102) has moved from the first position toward the second position, wherein the indicator is resettable by an operator from the second state to the first state by moving the indicator from the second state to the first state. the retainer (308, 1010) is configured to maintain the indicator (200, 412, 1008, 1908, 200A, 200B) in a first state within the slot (306, 720) when the barrier (106, 406, 1004, 1108, 1902, 2102) is in the first position; the retainer (308, 1010) is further configured to release the indicator (200, 412, 1008, 1908, 200A, 200B) into a second state] when the indicator (200, 412, 1008, 1908, 200A, 200B) is in the first state and the barrier (106, 406, 1004, 1108, 1902, 2102) moves from the first position toward the second position, wherein the indicator, when released by the retainer, moves, travels, rolls, drops, pivots, or otherwise traverses through the slot to the window under the influence of gravity; and the second state indicates the barrier (106, 406, 1004, 1108, 1902, 2102) has moved from the first position toward the second position, wherein the indicator is resettable by an operator from the second state to the first state by moving the indicator from the second state to the first state.