Things are found in the walls of old homes, quite frequently; most notably, childrens clothing and childrens shoes in homes dating back to the C.17th and C18th and on occasion, firearms. A few that I can remember, off hand:
An old abandoned one story wood structure on a heavily wooded/swampy piece of land that we used to hunt rabbits on. Local lore told of a unsolved murder happening at the house in the days before the CW. Property owners went to tear it down and a local gun collector was there and found a beautiful (and loaded and capped-except for one barrel) pepperbox pistol inside one of the walls.
Another one was a early colonial home on the North Shore of Long Island, which during updating, a musket with Brown Bess architecture and a Dutch hallmarked brass/bronze barrel was found, along with a large antlered hafted knife and a War of 1812 Officers Commission, inside one of the interior walls, all in beautifully preserved condition. I discussed this one with Earl Lanning who was tracking down people who may have come in contact with brass/bronze barreled longarms, at the time.
And lastly my middle brother was helping my father do an interior inspection of our churches steeple (C.1854) and while climbing the ladder, high up and in front of my father, found a beautiful 1861 Springfield musket and a Springfield training rifle, with a wooden barrel.
Just a note, in these older homes, walls were not built to any modern standards, as we know of them today. Floor boards were usually continuous and the studs of interior wall were just toe nailed directly into the flooring, irregularly, sometimes as much as 3 feet apart, but the stud was also a full dimensional 2"X2" or as big as 3"X3". Also, my 1854 row home in GA, has 4 foot spacing between the non-load bearing walls, so there was plenty of room to put things. In fact, some years back, a couple was converting two adjoining row home for a Bed and Breakfast and in the course of making a passageway to join the interiors of the two properties (National Historic District) and tearing out an interior wall, found the mummified, fully clothed and outfitted remains of a Union soldier, between the walls. The remains and artifacts were taken by GBI and after examination, given to a museum for disposition. I imagine (speculate) the soldier had committed some offense upon a local and just didn't show up for the next roll-call. Vigilanty justice? Murder? Self defense? An accident? Who knows. But what we do know, somebody didn't want him found and he wasn't for about 100 years.
I have a few more, but I'm already boring you. These old homes/building have never ceased to surprise me for nigh on 55 years. What's even more surprising, is that things are still being found today, pretty much for just a simple lack of curiosity over the years.