I think this had to do with real estate and inheritance laws from long ago. In the present day, title to real estate can be clouded for up to 50 years before it is clean. That is, unless the real estate undergoes a foreclosure or tax sale.
As 50 years is the break between two generations, in the handing down of lands, heirs have 50 years to reclaim land held by adverse possession, such as by banks or trustees, if they can afford the legal fees.
That's the Crack in the Liberty Bell.