Back in my metal-detecting days, I'd read of guys who worked the fence lines of old abandoned farms, etc. with their detectors. They said that after the Depression, a lot of people still distrusted banks, so they saved their bucks in "post hole banks".
They'd take a fencepost and cut a foot off the bottom, put their money in an old cast iron Dutch Oven, put it in the hole with the shortened post on top - nobody the wiser.
Dunno if it is an Urban Legend, as I never had the chance to find out- I was in California and they were talking about the midwest.