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Features such as this are built into Airstreams to make vintage Airstreams that much more desirable, serving as time capsules as well as travel trailers. Getting into inaccessible nooks and crannies usually results in the discovery of some historical artifacts. (Hopefully not grossly decomposed.)
Pacer included a variety of interesting artifacts, including a can of tuna that I was thinking about selling on eBay until I noticed that it was bulging distressingly and concluded it had better go to the landfill.
When I took the shower pan out of our 1980 Caravelle to gain access to a leak in the freshwater plumbing I found an interesting array of circa 1980 pop rivet stems, cigarette butts, and a candy wrapper.