It was some of that white beadboard I covered up with FRP in another unit. It was hardboard with a white finish and the finish wore off.
It won't work in the unit in question because I've decided the wallpaper, which goes up to about 12' in the corner is itself too old. Even if I put new material at the backsplash level I need to something about all the wallpaper.
I'm not crazy about wallpapering but it looks like it's in my future.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13