I'm in Bremerton, CRH. While my two gold ring day was at a public park right here in Bremerton, I've generally had better luck at permission sites. The parks and schools have been worked hard here in the distant past, but it's been a while for some of them and some can still produce clad and jewelry. I've had absolutely zero luck with silver around here, save for jewelry. If you subscribe to the theory that x silver is found for every y wheaties, I'm owed a freaking silver ingot.
So I'll go with the standard advice: parks, playfields, schools, and other public property. (For parks in Bainbridge Island, permission is required. It seems that anything goes for the rest of the county.) Do the research and focus on the older sites. The oldest sites in the county are on the National Register, so forget those. If you get tired of that, knock on doors. Silverdale, Bremerton, Poulsbo, and Port Orchard all have old neighborhoods. If you're going to work Bremerton, maintain your situational awareness. I had two "encounters" in one day at Evergreen Park after the sun started to go down. Things should be safer to the north and south, or during the middle of the day in the parks that see a lot of traffic.
What part of the county are you most interested in? I may be able to give you more information. (No promises though, particularly if it's something that I'm eyeing.) There is some history here, but not like what the east coast or California has.
I don't even remember the last time that I went to PT, so I can't help you with that. Kingston is not an area that I ever expect to get up to, but IIRC the oldest part of town is in the viscinity of the ferry terminal. Use the county's parcel search application (located here: https://psearch.kitsapgov.com/webappa/ ) to figure out the ages of the buildings in that area.
The Kitsap Historical Society put together an exhaustive (if somewhat poorly organized) book on the history of the county back in the seventies. They drew upon a lot of "tribal knowledge" from the old-timers of the era - the folks born right around the turn of the century, so the children of the original settlers in most cases. It's been out of print for a while and is hard to find, but I notice that the KHS is currently selling a new revision; it's still a bit pricey, but at least it's easy to get hold of now. If you can't or won't pay for it, your local library should have a copy. Read it. Some of the information in there is basically forgotten, even by the current generation of elders.
With that out of the way, Poulsbo originated right around where "Old Town" is today, so start there and check dates. A few of the homes in that neighborhood date back to 1900 or so. Use Google Earth or Google Maps to find likely-looking houses, then get their age with the county's website. I like to actually print up a screen capture from Google Maps and then manually date each home on it; not only does that show me which doors I want to knock on, but I can also refer to my notes and tell the homeowner exactly how old their home is and (if it was mentioned in the KHS book) some of the history behind it.
Sadly, Poulsbo has changed a lot from the early nineties when I lived near there. Some of the spots that I'd hit are gone now. I'll give you a few freebies though, since I'll likely never be that far north:
Freebie #1: Old homestead, just off Hwy 305:
It doesn't look like much, but I remember that there were a number of old buildings there back in my teen years. Here's an overhead from Google Earth from the early nineties:
That looks like a house and a couple of barns to me. I believe that one of the Vetter brothers originally built the place, although I may be wrong about that. The neighboring Vetter road is a bit of a giveaway though, as the property predates the highway and Vetter Rd. would have been the only access before 305 existed. The property is owned by Edward Rose Millenial Development LLC.
Freebie #2: There's another old place just south of there. If you're driving south on 305, look to your right when you're near Central Market. You will see the ruins of an old house up in the woods there. I can't tell you the age for sure, but I attended a party there in '92 or so and I vaguely remember it being a very old house. I'm somewhat curious about how it wound up in its current state, as it was abandoned and in bad shape when the government sent me back to the area in '98. This one is owned by Chinook Group LLC, a Bremerton-based company that operates out of one of the owner's homes. This site is badly overgrown.
I have not obtained permission to hunt either. That's on you. Both sites are old for the area though, and I'll bet that neither has been hit hard. I wouldn't be entirely surprised if one or both have never had a coil over them at all.
If you want more places, you'll have to find them on your own. Use Google Earth and the KHS book to locate potential sites and then date them with the county's website. That's really all that there is to it. You'll find that metal dectorists tend to get very cagey when asked for specifics, as good sites are hard to find and a lot of research may be involved. In fact, the only reason that I gave you those two was because I have mixed luck at homesteads and I can't be bothered to go to Poulsbo to hunt them.
Okay, one more Poulsbo freebie, sort of: Liberty Bay Park, the parking lot, and the other land between the buildings on the west side of Front Street and the water is all fill. Check out the old photographs (several are in that book that I mentioned) and you'll see that a lot of those buildings used to have piers coming out of the backs of them. If that fill is ever removed for some reason - and I really can't think of a good one - I'd work that place hard. That fill-in occurred around 1960 if memory serves, so it predates reliable saltwater detectors. A lot of people walked up and down those piers from the late 19th century to the middle of the twentieth. What did they drop?
Click and hold the left mouse button to drag the map around. There are buttons to zoom in and out at the upper left hand corner. You can also simply double click to zoom in.
Once you're over the property in question and have zoomed in enough to see the tax ID, click on it. A window will pop up identifying the taxpayer and showing their address. There will be a few tabs under this block of information. Click on "Assessor and Zoning". This will bring you to another screen showing the property report. There are a number of colored tabs at the bottom. Click on the orange "Building Data" tab and you'll go to yet another screen showing details on any buildings on that lot, including the age, size, etc. (Hint: there will also be a code next to the building type showing whether it's fair, average, good, etc. This gives you a hint about the building's quality and how well it's been maintained.) There are plenty of other useful tabs in this program that can help you in a variety of ways, but Building Data is probably the most important for our purposes.
If you think that this is a bit complicated, you should have seen the clunky, buggy, counterintuitive load of crap that the county used to run until recently. It's way better than it used to be.
This program will only list the ages of buildings that are not on military land. Military lots will typically show up as not having any buildings at all, even if they do. If a building has been "written off" (partially destroyed, uninhabited, will not be fixed), the lot may show up as undeveloped - the county does this so that the property owner isn't paying taxes on a building that's not really a building any more. In these cases, by using the Google Earth timeline tool in conjuction with the sales history tab, you can usually at least figure out if there used to be a building there and when it was removed.
Also, once again...read that book. Take notes while you do, particularly when addresses and historical useage are discussed. That's exactly the sort of thing that you want to know, but even the old-timers don't remember this any more. The people that told these stories are now all dead, so we're left with this book of their recollections.