1968-S Lincoln Bonanza

I picked up 10 rolls of cents at the bank this past weekend and apart from pulling a fair bit of copper, coming across a few 1950s wheats and an 1898 IHC, I strangely found eight BU-red 1968-S Lincolns. The 68's were not found together in one roll, but randomly distributed throughout the 10 rolls. The cents were not customer rolled. I'm guessing they were broken out of the same roll (?). But what are the odds that almost 20% of them would end up in 10 random rolls at the bank? Perhaps I am just easily impressed, but has anyone else come across a fair number of the same year coin (S mint mark) in BU grade from such a small sample?