sounds like you're an accomplished turf hunter. There's a contingent of hardcore turf-hunters in So. CA/Los Angeles area, able to eak out silver from the park there too. But .... naturally .... the parks aren't going to be as old as your Chicago experiences. The few parks out here in CA that *might* be as old as the 1860s, tend to be now in the more blighted parts of towns, and thus filled with wino-caps, zinc, aluminum, etc....

As opposed to portions of the upper mid-west, or back east, and there's still some mid 1800's sides of towns, where ......... TO THIS DAY, they remain "upscale". But out here in CA, "urban flight" to the suburbs in the 1950s, seemed to create blighted districts of our older down-town parks. And go figure too, that all the migration was from east, to west. Meaning that a city here that had a population of ... say .... "5000" in 1940, now has a population of 50,000 now! But in the upper midwest, and towns back east, a town of 5000 in 1940, STILL has 5000 now

Or heck, even got less people, in the case of the some of the upper mid-west (where agrarian lifestyles gave way to mega-farming techniques, drying up little farm-towns).
So it seems that most of the silver being farmed from the parks down there, is of the merc and roosie caliber, with an occasional barber or IH thrown in. I know of some parks up my way where I can reliably get a barber or two with each effort (and usually the desirable S mints, being that you're in CA now!

) But not sure how consistent that is in the L.A. area, since that place balooned out 100-fold, population wise, from the 1940s to the present.
The best way to hook up with turf-hunters down there, is to get on the "kinzli forum". That's where all the CA guys seem to post/read. To get to the main page, you have to be a member. So you'll need to take the time to pick a name and password. But once there, you'll bump into fellow turf hunters.