At the conception of the beaver tail tabs they were called "Pull & Toss Tabs" and that's exactly what everybody did with them, they were small, harmless and people just pitched them on the ground, I doubt that 1% of them when the product was opened ended up in the trash. I still find these things sometimes hooked together to form short chains. On canned beverages the pull & toss were in use from 1965 until 1975, then came the square tabs.
At the conception of the square tabs they were called "Stay Tabs" someone finely figured out that the pull & toss tabs had become a MAJOR litter problem, so hey! they made the "Stay Tab" litter problem solved!! NOT! most folks were so used to pull and toss that they had a habit of tossing the older tabs, so they opened the can and then broke the stay tab off and tossed it on the ground. On canned beverages the stay tab came to be right after 1975 and are still in use today.
Both tabs in there existence took on several design changes, the early pull & toss was a little dinkier and often times the ring would come lose from the tab before it pulled the tab off the can. So, a little later on the tab was beefed up a good bit and functioned much better. and yes! I've heard the same thing about some alloy changes in them over the years. The most problematic of the tabs is the tail of the pull & toss tabs, when left attached to the ring they would curl up, well of course each curl is as different as my finger prints vs HighPlainsHunter's" . These tails messes with the detection field coming off the coil in sometimes very strange ways, some common problems I have them is,
Throwing the pinpoint off,
ID'in much higher than they should for a tab,
And they normally have an excellent audio report that makes it very difficult to hunt the lower conductive range and work around them.
And don't confuse the modern pull rings from a planters peanut can with one that is from the MUCH older beverage cans, most of the time the peanut pull rings will stay attached to the lid so they are pretty easy to tell. The reason why I mentioned this is because identifying the early pull & toss tabs is one way I judge depth and age of an area. Those dinky pull & toss tabs at a 5" (any average depth you find them) average speaks "1965 to maybe 1967" If I know the area has had public use back to 1935 then I can get an idea of the depth of the silver and the depth of the oldest fresh drops.
Example, a 1935 dime dropped in 1935 would have very little wear on it, making it a 1935 fresh drop, the more wear it has the more upward towards the pull & toss tabs it will be.