births1860.2001-2227.ia7out = 83 = normal run
births1860.2001-2227a  = 62 = with date check of books 
births1860.2001-2227b  = 46 = with date check including 0 on books with no date
births1860.2001-2227a1 = 21 = books in core but not a
births1860.2001-2227ab = 16 = books in a but not b