The last two digits are for sorting out duplicates; for example, there are four Bob (or Bobby) Adams in the Lahman database, adamsbo01, adamsbo02, adamsbo03, adamsbo04. They correspond to the four Bob Adams found by searching Baseball Reference:
http://www.baseball-reference.com/pl...ue+or+Team.y=9
By the way, you may notice that B-R seems to follow this player name/numbering scheme. That's how I noticed Hank Aaron is actually "aaronh
a01" in the database; he's listed that way in the address for his B-R page:
http://www.baseball-reference.com/a/aaronha01.shtml
A little tip that I read here recently . . .