Possible Mercury Dipped/Plated Coin

Even before I finished reading your post I thought "mercury".
And it appears that you know the dangers of handling mercury; absorption through the skin is one way of poisoning yourself.
You can heat the coin and vaporize the mercury BUT breathing mercury vapors is worse than absorption through the skin.

If you are close to a college you could go to their chemistry department and ask for a favor.
"Please decontaminate this coin for me."

I'm pretty sure it's Mercury. I'm quite familiar with how Mercury looks like. Oil looks different. I've had a couple of coins covered in oil and it doesn't make it look this dull.

I guess that's what you actually get from spending the first 15 years of your life growing up in an LEDC. Regulations aren't that tight (yet). You could just pop to the nearby medical supply store and get a Mercury thermometer well into the 2000s (alchohol ones weren't common back then). And I used to break them too just so I could roll them around......at least I'm not mad. Or at least I think I'm not mad.
In the 80s students are given a sample of Mercury to put on their hands and swish them around just to know what it feels like, as my previous math teacher told me (here people use Gallium, which sucks because I can't get it to melt). Even primary schools have samples of elemental Mercury in their labs stored between two petri dishes held together by masking tape so the students can see what it looks like (I handled this one in person). Mercury thermometers are still very common nowdays, even in school labs. I used one when I did my IGCSEs on Dec 2012.
One thing I still remember before I left to come here, pretty recent, less than a year ago. My brother broke an old Mercury thermometer by accident, and we all (dad, me, 3 younger siblings) were rolling the thing on the floor to get all of them together while mom is looking for something to scoop the thing up with.
And I'm quite familiar with aluminium coinage too, it's just too bad I don't have a full coin now to compare it with. Just the edge of my Kelapa Sawit coin. Should've brought some when I went home last Christmas. They're ridiculously light.

Since I had to do a project on the Minamata Bay disease in 5th grade I learnt quite a bit about Mercury, and remained quite fascinated with it. I read an older thread in the Canadian forum and found out about Mercury dipped coins and searched the forum for more since I found it quite interesting. Never thought I'd own one myself, though.

Some photos. Sorry for the glare on the plastic, I don't know how to get rid of them. But it just shows how dull-looking this coin is.



With other Jefferson nickels. Light source from top of pic, sorry. All the glare is from the plastic. There's no white spots (showing reflected light) on the coin, unlike the others.



Side by side with the most tarnished Jefferson nickel I have (you find quite a few CRHing here). I have a 1938 one (which I sort of forgot to put in the pic on top) but it's not this tarnished (quite oddly). You can see white spots on the one on the right but not the suspect coin. The second photo had added light coming from the left and still no white spots.



If anyone wants higher resolution pics I will upload them in a host and link them. All photos will be taken with the coin inside the plastic because I don't want to take it out again.

I have put a label on the plastic with a warning (in case some person tries to because they think it's just some boring old money):


I'll probably keep this coin, though, I find it rather too dangerous to release it back into circulation if it is Mercury. Who knows how many more people are going to handle this coin.
And why would someone dip a Jeff in mercury? Some people do anything...

Is there a definitive test (without ruining the coin, so no 'take a hacksaw and chop it in half' please) instead of just observation by sight?

I doubt the plastic bag is a real barrier. But mercury does combine with other metals, such as in old tooth fillings. You could check to see if it is a real hazard. Buy really, it is worth 5 cents. Any cure would cost more, so I would take it in to a hazardous materials collection point and say I lost five cents. Where can that be done? Call your waste management for your area. If they do not want it see if a local university can take it for disposal with other materials from the chemistry department.

There are so many things that could cause that effect. For one thing there are numerous variations in oils. Also, many people use cleaner waxes on coins. Might be just someone using different cleaning materials. So many people use Olive Oils, cooking oils, etc. on coins or just on their hands and that gets on coins. Not sure if in your case Mercury but you may be just getting a bit carried away with all the hype about Mercury on coins. Just drop it off at a coin store, police station, fire station, etc. and tell them of your opinion. If you do, don't bother to ask for another Nickel in exchange.

Here in the USA many cities tell residents to contact the fire, police, etc for such things. IF not sure, try it anyway. Regardless, they should take it and better them doing something with it than you.
As to your headach. When I was in Chem classes in high school and college, I handled Mercury all the time. I've also been a Chem lab teacher in college. I also have made lots of toy soldiers with Lead. I've used Mercury for all sorts of things and Lead too. I'm still alive, hopefully well, nothing wrong with me that I know of YET.
I really think your headach is from worrying about the Mercury, not the Mercury itself.
Of course there is one thing you could do. Simply hand that Nickel to someone you hate.

I'm sort of new to the West culture so forgive me if I sound kind of dumb sometimes. I come from Indonesia where things are very different. First 15 years of my life there before coming to Canada to study abroad.

Tell you what, I'll bring the coin to the school chemistry lab tomorrow and see if the teacher can do something about it.

There's something wrong with my connection now I think. I can't seem to load YT videos. The page opens, everything else is there, but all I see is a black box where the video should be.

It looks to me like a normal nickel. And even if it was rubbed with mercury the mercury would have amalgamized with the nickel so and outgassing would be fairly close to zero. And mercury really isn't anywhere near as dangerous as people make it out to be. Amalgams even less so. I've had mercury amalgam fillings in my mouth for over 40 years and as far as I can tell they haven't hurt me at all. And they aren't just subject to outgassing but also leaching from eating acid rich foods and the acids produced by saliva and mouth bacteria.