I use the following tiers: 1) 2x2 flips in folders and binders for KM-code series, curios, precious metal coins, circulating commemoratives 2) 2x2 flips in boxes for lustrous and old coins 3) ISO 9706-compliant copy paper envelopes, pockets or rolls for bulk storage by KM-code and country, with markings for incomplete sets (years and number of examples per year). Rolls for excess in another box. With flips I store multiple small coins in large aperture flips with 2-4 coins of consecutive years of the same KM-code and place in a binder book or folder as part of a KM series. I used to use album pages for coins, but then I read about possible vinyl residue being left on coins, so I've fully switched to flips. However, I've thought of cutting flips to fit album pockets with the smaller coins. Haven't tried this yet. I've also entertained the idea of cutting the sides off of the smaller-aperture flips to fit two in the same page pocket.