Rip was using Riker Mounts - the only experience I have had is using them for botanical or insect specimens. Behind is a cushiony material that presses against the glass when empty. The specimen is gently pressed against the glass by the cottony material without smushing. The box is kept tightly closed by a set of straight pins the line up matching holes. Whether the fiberfill is acid free and the glass UV protecting--you would have to contact the manufacturer to get that information.