RESEARCH !!!!!!!!!!!It's all in the location !!!!
Any place that had people on it doing active things back when they carried silver coins in their pockets is still likely to hold a few old coins...even if it has been hunted to death.
Old maps of your area will show parks, ponds, lakes and sometimes fairgrounds that may still be there.
Maps will also show where the city limits were, and most cities have grown considerably since the 1950's and 1960's. Recreational areas that were out in the boonies back then, might be well inside the city now.
I have 16 maps of my area--from 1939 up to 1985. I have a 1955 map that shows a park in the city--according to the city website--the park was aquired by the city in the 1952, and is still in use today. It has been hunted hard over the years.
My 1939 map shows the same park--outside the city limits. So the park was in use at least 13 years before the city aquired it. Using this information I very slowly searched sections of the park and found old coins ( silver, wheats, buffalo nicks, and a Indian Head cent) hidden deep under layers of bottlecaps, pulltabs and other trash left from years of use.