Here is R163 with a cancel that stands for Steamer Gold.
Now the "Str" was used either for Steamboat or Steamer", then was shorten to fit on the cancel as you can clearly see.
The Steamer Gold was built in 1883.
Later sold to the Petaluma & Santa Rosa Railroad Company.
If you want to read more about this Steamer, look up Petaluma history.
The photo is the Steamer Gold as you can just make out "GOLD".
Stampmaster

