When I showed my British partner my photos, he pointed out that the "heart" is actually a sort of logo for the British Standards Institution (or BSI). And of course, when I came home and looked it up, I saw that he was correct.
The BSI Group was founded as the Engineering Standards Committee in London in 1901. The "heart" I saw is their "Kitemark" created in 1903 as a symbol to identify products made to meet BSI' specifications. It was called their "Kitemark" because the shape of the graphic - an uppercase B (for British) on its back, above an S (for standard), enclosed by two lines, looks a bit like a kite.
The Kitemark became a registered trademark in 1903, making it one of the oldest product marks in the world still in regular use.
I prefer to call it a Heartmark, because the heart is a much older (and prettier) mark, also still in regular use, I believe...
Happy Valentine's Day everyone.