I keep it in an album. If wanna save budget, try to put it in an container and put some silica gel in it. That to prevent air moisture. It will cause banknote become yellowish.
In another hand, book just estimate price value, it does not always accurate.


Banknotes Grading : UNC,AU,EF,VF,F,VG,G,FA,P
Coin Grading : PROOF,FDC,BU,UNC,EF,F,G,P