Banknote collections for some is a very serious thing and actually varies in every person. Most of their collection are based on banknote signatures, wherein it involves every presidential and BSP governor signature of every denomination in every year, but not limited, it all depends on the collector should sample he decide to focus, say to an specific denomination or year.
For banknote signature collectors out there, here’s a table of signature varieties from 1949 up to present (CBP & BSP). Reference for English series to early BSP New design series. Hope you like it!