Just happened upon this photo:
http://caltrafficsigns.com/pictures/displayimage.php?album=11&pos=3
This appears to be today's 160/12 junction east of Rio Vista, albeit much earlier in time. I've never seen the bear shield with the "COUNTY HIGHWAY" designator though...I wonder if this was used only upon the initial signage of state routes, or if there are other examples of this out there.
(Which once again makes the continued Route 39 Fullerton gap even more egregious. :pan: )
that 12 is the only county bear I've ever seen, and the amount of knowledge that I have about it can be fit into this invisible pink thimble.