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?