There are exceptions for some West Coast cans where low profile tops were used in the late 1940s. Crowntainers were used between 1940 and about 1953-54. There should be a small box with patent information. WARNING: A lot of fake conetops have flat bottoms and high profile spouts. Flat top 15 and 16 oz cans came into use starting in 1953 so a flat top 16 oz can would date between 1953-1964.
The original low profile cans had flat bottoms and inverted ribs on the top. Krueger Brewing made the only 16 oz cone top in about 1940. The ale was a tough can until a couple hundred were found in a barn in Vermont.
Before that date brewers had to include a tax statement.
Note: A handful of the very first cans from 1935 do not have this statement.
If you can has the "Keglined" logo on it and if it's from that period, you might be able to read the date code. The earliest pull tab (an Iron City) was sold in 1962. Then it dates from the mid 1970s until the early 1980s. Does it have opening instructions on the side of the can showing how to use a church key?