Unfortunately the dice can not be stored. The old polyurethane foam braks down an dreleases, amoung other things, formaldahyde and urea/uric acid. These will over time eat into the plastic and cause permanent damage. I have several older pairs like this my self. Adhesive tape left on dice for long periods of time will also eat into the plastic.

The old laudeman book shows a pair like this but without the smal number above the logo. Listed as LV0878, early 70s, and valued $26-$35. The Olson & Johnson book shows a piar (also no small numbers above logo, listed as L3515, 70s, $21-30.

Laudeman's book was published in 2000, and the newer book in 2004. The foam damage will reduce the value but they are still a nice pair.