Another area where foam rubber was used was in the inner lid seal of early Scotch 3M blue plastic video tape cases made for
larger 12 1/2 inch reels. These cases were used quite a bit with the 379, 399, and 400 videotape series beginning in the 1960s thru the early 1970s.
This type of case was replaced with an updated blue case which used a round synthetic rubber O-ring inner lid seal.
As can be observed, the foam rubber inner seal decomposes to a fragile state and migrates to the reel and tape when the case is picked up or moved.
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