This rusted piece of metal someone found in a river:

1

"It's the tip from a .223 caliber rifle."

This metal container with two spouts was found hanging in the woods of Minnesota:

2

"This is a very primitive oil lamp, usually called a 'yellow dog.' Used outdoors on oil rigs."

This plastic, pen-like electronic device with a cable:

3

"Old barcode reader. Unlike modern devices, the user had to slide the point (LED + photocell) across the barcode."

This pointed piece of metal someone found in a garage:

4

"It's a picker arm assembly for an International Harvester potato planter."

This small metal device with a dial that moves its prongs closer together or farther apart:

5

"It's for opening the case of a watch."

This set of tools in a wooden box found in an antique store:

6

"I have this exact tool, a Blake coaxial indicator. It's a quality product, very useful. Cheap clones killed the Blake company, and now you can only find the low-quality knock-offs."

These pair of wooden items with handles and crossed bases:

7

"Handle/base for basket weaving. Like this or this."

This ornate piece of brass with a lid-like piece that closes when pushed down:

8

"It's a brass billiard pocket, similar to the one in this link."

A heavy metal black box with a gauge and two clamps on top that was found in an old paper mill museum in Wisconsin:

9

"It's a paper tester. The paper goes inside the clamp parts and measures the pressure required to break through the paper."

This little pottery cup with four holes along the back side:

10

"Looks like an herb stripper."

These flat objects sticking out of the ground in Germany:

11

"Drainage wick method to dewater and firm up foundation and stabilization."

This big metal cone being used as an ashtray in an old mining town:

12

"Conical slag mold."

This decorative-looking protrusion on the wall in an apartment in San Francisco:

13

"That is a cover over an old wood stove exhaust vent. When the stove and pipe were removed, they covered the hole with this plate. Add layers of paint over several decades, and this is the result."

This tiny, ceramic cup with a slot cut in to one side:

14

"Dispenser for postage stamps on a roll."

This wooden, electronic black box with two cushioned pedestals inside:

15

"It is an automatic watch winder. For watches that self-wind, you put them on those things, and it shakes them or rotates them so they wind. I did not do any research into how the device operates, but it may actually have a timer and only rotate for like 10 minutes a day or something."

This stone block with a wooden handle found on an old farm:

16

"It appears to be a tool for waxing cross-country skis."

A black plastic item with a green, fuzzy side that someone found magnetized to the bottom of their dryer:

17

"Fish tank algae cleaner. A matching one goes on the inside of the tank, and the magnet allows the user to move both pieces and erase algae off the inside glass."

This black, hollow tube someone found while diving near old military bunkers in Ireland:

18

"It seems to be a carbon electrode for an anti-aircraft searchlight."

This black metal box on the outside of an old building:

19

"I believe it’s an old bank vault alarm. Here's a picture — it’s a newer version, but the same idea…the external/outside siren for a bank vault alarm."

This real horn with some kind of tool that's embedded into one end:

20

"Cigar cutter."

This thick metal cylinder with a Polish historical figure on it:

21

"This is a die for a medal. The image is Stanisław Wawrzyniec Staszic. Here is the only example of the medal I could find online."

This metal tool with a wooden handle and copper cylinder:

22

"Plough gauge for leather working."

This metal rectangle covered in holes and number markings:

23

"This is for cigar wrapper bands. Certain brands used codes, and using this gauge, you could tell the date it was harvested and made."

This flat metal piece someone found in their garbage disposal:

24

"It's one of the feet from a metal colander. We have a colander that now has two feet because one, which looks exactly like this, came off. Check for two small dots where it was previously welded into the colander, and then check your colander for a missing foot."

This metal, funnel-like item with a wooden handle:

25

"Antique laundry agitator."

This plastic piece drilled into power poles in the Northwestern part of the U.S.:

26

"It's where they have drilled a deep hole in the wood to inject chemicals to help prevent rot. That is just a plug for the hole."

And finally, this recessed opening on the side of some bungalows in the United Kingdom:

27

"Larder vent. Older Victorian/Edwardian houses used a large stone 'cold slab' in a cellar to keep food cold and safe from vermin, but if you didn't have a cellar, then a convectively cooled larder was the next best thing. At least some larders also had a traditional cold slab in them."