.............................................................EUREKA!
That fine line that rises above the house on the hill
is an early electric light mast!
detail from HERE
The house (and mast) are visible in a photograph taken at The Plaza in the 1890s.
[link to the complete photo is below image]
detail /
USC
I know that we have discussed this mast on NLA. (but I wasn't able to locate the old posts)
The lighting mast is even illustrated on this 1889 map.
waterandpower...............................................................................................for search purposes: William Workman property and vineyard, Boyle Height
Of course this doesn't solve the location of my 'mystery' eBay photograph.
You can see the mystery photo (again)
...HERE
.