The DoB entry in the databank is incorrect for Mike Mattimore (ID 8983).
It's currently set as August 1858, 1859. Obviously, this is incorrect.
Retrosheet lists August 1858 (no day known), so this looks like an update
entered in the wrong field.
New correct line (sorry about the word wrap):
8983,1858,8,\N,"USA","PA","North
Bend",1931,4,28,"USA","MT","Butte","Mike","Mattimore",\N,"Michael
Joseph",\N,160,\N,"L","L","1887-05-03","1890-07-21"
Regards,
Derek