The inside door on my 79 has the same textured vinyl covering that makes up the rest of the interior skin.
I'm trying to imagine what could be done to it to make it look like phenolic. I guess I'm just not that imaginative.
Have you tried gently prying at a corner to see if maybe it's just old wall cladding?
1975 Argosy 28 "Argosy"
1979 Excella 500 31 "Betsy"
1992 Lincoln Mk 7 LSC
2003 Dodge 2500 Cummins "TowHog"
"Lucy Loosehair" the cat - Airstream mascot
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