On Thu, 17 Dec 2015 13:46:53 -0800 (PST), Murmansk
wrote:

The suggestion about the picture rail having been removed is interesting but my gut feeling it's not that. This is however the kind of house that might have had a kind of plate display shelf in the hall downstairs. I don't think it's the era for a picture rail.

My parents' 1930s semi had picture rails, and cavity walls.