Can't see much detail in those pics, except that it was indeed once mounted on a chain - you can see the damage where the mounting has been broken off the top.
The key thing indicating this is not an actual coin is the lack of a date. Vatican / Papal States coins from the 1800s usually bore two dates, the AD date and the regnal year of the Pope.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis