You have a picture of a metal street cover on your "What is It?
Where is it" page that says "UW Co" wondering what it is - I
have some answers. "UW Co" refers to the Union Water Co.
of California which existed between 1910 and 1921. You can
find another cover with the "UW Co" marking in Berkeley on
Euclid Ave. across from Berryman Reservoir.
The metal caps are the covers for the valves that EBMUD and
previous companies used to turn off the flow in the mains. You
can see a chart of about 18 early companies that flowed into
EBMUD soon when it formed in 1923- in the EBMUD lobby on
11th street.
In the past year or so I have been making a search for valve covers
that are marked with earlier companies - previous to EBMUD. Now
I have pictures of about eighty.
Charles Bucher