Ok, Well...yes. curiosity killed the cat. I'm not one to drain metal cans, but I just punctured the bottom edge of the can with a very tiny hole. As soon as the air went in...pop! The can popped right back. No dent. I won't do this to all of them, but now its documented here on this site. I think Advertologist is right..thinner, metal cans such as this one caves in compared to the thicker cans made prior.
IMO - some of the later versions of the metal cans are made a little more "economical" than the earlier versions which I believe causes this, there made so economical that this problem is unavoidable & the only way too correct this is too drain the can .. ...
95 + % 0f my oil cans are full and have had some for 30 years or more and are in a temperature controlled garage which only gets to 40-45 degrees in the winter at worst & most typically 50 degrees in the winter and probably 70-75 in the summer . I have never experienced cavitation on any of my cans .Gets real cold here in the winter. Don't understand what is happening to your cans.
I have this lighted Sealed Power clock for sale. It is an original clock, but has a crack in the glass face. I have epoxyed it back together and it is stabilized and probably stronger than before. You can see the crack when standing close to it but its not visible from a distance. Price is $300 delivered to Iowa Gas.
See pic. Penn-Drake metal oil can. A small '65' a long the bottom edge. Could this indicate a year of 1965? I would assume 1965 was getting close to the last of the metal can era? Thanks for any insight.