Looks like a tiled counter to me. In southern California (and I’m sure other places but that’s where I first encountered it) in the 60s and 70s a lot of kitchens started being made with tiled counters. Think small bathroom wall tiles put on the counter surface rather than floor tiles. I don’t know why it caught on, because they’re uneven and impossible to keep clean. But a lot of old rentals/homes still have them if they haven’t remodeled since then.