Car seals on carload shipments of explosives for transshipment via float or barge in Baltimore must not be broken, except as authorized by the federal regulations, until car float is alongside of vessel on which explosives are to be loaded, and only then when it is necessary to begin unloading the car. City Code, 1927, art. 15, §70 1950, art. 11, §72 1966, art. 10, §71 1976/83, art. 10, §71 Ord. 13-336