Hi,All four YALE locks are keyed alike,Marked on bottom of cylinder “1616”,two keys,numbered “1616” work all 4 locks.The “IND” stands for Independent division.The NYCTA has 3 lines,The “BMT”,“IRT”,“IND”.I know about the history of the locks,I was only asking if they were common or rare.Thanks though,for your answer,Its nice to know other quys look at this site.