The list above is a good generalization, but you can't accurately date oilers by the type of spout.
I've seen handy oilers with lead spouts that were newer than oilers from the same oil company that had plastic spouts. The were even made by the same can manufacturer. Although they were likely made in different locations.
Things that will help you narrow down the dates:
Can company manufacturing codes,
oil company logo,
product logo,
can company logo.
Wanted: Gas pump globes:Sinclair & affiliates, IL companies. Ripple bodies. Anything Sinclair, Stoll, Pierce, 4 Bros.
http://www.lastgas15.com/