d2dd4b77___Stamp_Collecting_Accessories__Description
[Accessory] Stamp Mount [Price Range] $8 per package (>6 mounts depending on size) of 215mm mounts average [Description] 
They are the accessory of choice to store and affix stamps that are expensive and/or mint. Hinges have the disadvantage that hinge marks are left behind on mint stamps. Further, collectors prefer MNH (Mint Never Hinged) stamps and which explains the premium associated with them.
One Family's Blog: Stamp Collecting Accessories
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