Most of the time when someone posts a picture or two to the r/whatisthisthing subreddit, they expect a few wrong answers followed by someone miraculously knowing the correct info.
Sometimes, we just want to believe something so hard that we make ourselves do it.
In a comment, he explained that he was struggling to even figure out what keywords to use in a Google search.
So if the master identifiers on Reddit couldn't help, he would be out of ideas.
Admittedly, I wouldn't have known what to search for either. Like "acorn spikes brass old?"
When I did a reverse image search, Google thought it was a "bead."
Which was the right idea, but who could have predicted that the first answer would be "abortion device?"
Wait... never mind. I just had the mental image and will never unsee it again.
Attach string to ring, stuff the acorn up there, pull string. String pulls ring, spikes come out. Ouch.
It's also worth noting that the subreddit has strict rules about staying on topic and answering the question posed.
The moderators locked the thread down and deleted most of the nasty comments.
Redditor I_Me_Mine made note of this when posting the correct answer.
Finally, they put everyone out of their misery and revealed what this object actually is.
Which is actually pretty nifty, but will likely take a bit of explanation since most people don't wear pocket watches anymore.
If someone tried to pickpocket you, the chain would tug the ring and the spikes would get caught on the lining of your pocket.
And then presto, you've suddenly caught the thief in the act. Like I said, it's pretty cool.
As for why they all seem to be acorns, I'm not sure. Presumably it's just decorative, but if so, you'd think multiple styles would have been available.
At least, my nerdy, steampunk-loving heart thinks it is.