In the 1930's, oil companies began marketing oil in cylindrical containers of fixed volume, to protect the contents from contamination, to ensure quality and to provide oil in convenient sizes for motorists. You had to puncture these tins to open them, and pouring the contents often meant getting oil all over the place. So, creative minds set about inventing spouts that could be easily inserted into the cans. Below are some examples.
The top one was made by the Sterling Auto Manufacturing Company of Chicago. (Another company by the same name, but with headquarters in New York City and a plant in Hebron, CT, briefly made the Sterling car from 1917-1919. Apparently, of the 30 cars made, all that remains is one horn.) The second spout was made by "Cantapper" and was stamped "For oils, liquids & juices." Better not mix them up. The last spout was made by the Swingspout Measures Company of Los Angeles. The patent drawings for, respectively, the Swingspout and Sterling spouts are also shown below.