How old is this guide sign?

[NE2]

US 101 northbound in Ukiah:
http://maps.google.com/maps?hl=en&ll=39.15717,-123.19768&spn=0.015174,0.033023&gl=us&t=m&z=16&layer=c&cbll=39.157255,-123.1977&panoid=6_WENEnYs6fgsPxz6itNxQ&cbp=12,39.5,,2,6.86
It looks more cracked than the average California sign.

[myosh_tino]

US 101 northbound in Ukiah:
http://maps.google.com/maps?hl=en&ll=39.15717,-123.19768&spn=0.015174,0.033023&gl=us&t=m&z=16&layer=c&cbll=39.157255,-123.1977&panoid=6_WENEnYs6fgsPxz6itNxQ&cbp=12,39.5,,2,6.86
It looks more cracked than the average California sign.

I don't think its that old.  There are numerous signs in Santa Clara County with cracked sheeting, mostly on the county's expressway system (Lawrence, San Tomas, Capitol, Central, etc).  These signs were installed no more than 10 years ago and have weathered badly.  The sign in your post seems to have suffered the same fate as the ones I see all of the time in the San Jose area.  Maybe it was a batch of bad sheeting.

[J N Winkler]

I would estimate 30 years, not on the basis of the cracked sheeting but rather on the horizontal rows of rivets near the top and bottom borders.  In my experience, on newer signs the retroreflective sheeting is lapped over the rivets.  In fact, visible rivets are usually a sign of opaque coated background, but I don't think that is the case here since OCB doesn't craze in the same way.

[agentsteel53]

I would estimate 30 years, not on the basis of the cracked sheeting but rather on the horizontal rows of rivets near the top and bottom borders.  In my experience, on newer signs the retroreflective sheeting is lapped over the rivets.  In fact, visible rivets are usually a sign of opaque coated background, but I don't think that is the case here since OCB doesn't craze in the same way.

I wonder if a) the retroreflective sheeting cracked and fell off the rivets, or b) the reflected light makes it look like the rivets are on top.

OCB indeed does not craze like that.  there are signs from the 60s around here with the background just fine, and a retroreflective foreground almost completely gone.  (a ~1959-63 standard called for retroreflective border and button copy legend - so now there are signs with no border and button copy legend!)

I'd say late 80s to early 90s because retroreflective-background signage from before then is very hard to find in California.  as in, I cannot think of an example offhand since the 1965 experimental sign in Needles with a patch over US-66 was removed several years ago.