I happened to notice this symbol:
on a utility pole in a photograph from 1906.
What's the meaning of that symbol?
Is it a simplified logo of the Portland Railway Light and Power Company's logo? According to this site, they took over the electric services to some customers in Salem in 1906 (see below)
1906 :Portland got it's first movie theater. PGE merges with Portland Railway Company and the Oregon Water Power & Railway Company to become Portland Railway Light & Power Co (PRL&P) - the owner and operator of city and interurban electric railway services; PRL&P purchases tow power companies and takes over electric service to Washington customers in Vancouver and Oregon customers in Salem, Mt. Angel, Silverton, and Woodburn. Cazadero/Faraday Plant
It looks like a watermark or something similar, either applied on top of the photograph itself or added at some point during the process of converting the photograph to digital format. It doesn't retain the same shading that's on the tree itself (in particular there is a small shadow that would run over it if it was actually a part of the original photograph). Also, while it's more or less centered on the tree, it's not exactly centered and one would expect that the triangle shape would be ever so slightly distorted by the curvature of the tree if it was, indeed, sitting on it (in fact, it looks like it's "floating" in front of it, which is why I think it's an extra-photographic artifact). Tt's also located along the left-hand margin, not an out of the ordinary place to put a mark like this, and looks to me to be a brighter shade of white than anything else in the picture.