My strong guess is that your "dime" is actually the same size and thickness as a nickel, because .................. it IS a nickel. The "V" is of course the Roman numeral meaning 5.
In addition, it's not made of silver, but an alloy of copper and nickel, AND it could not have the so-called Mercury design because that wasn't introduced until 1916.
What you have is called a Liberty nickel. 1911 is a fairly common year: In worn condition it retails for about $3. With moderate wear, about $10, and with almost no wear, $30.
Sorry, no US dimes were struck in 1991 with a V on the back
Back in 1903, the nickel was called, the "Liberty" nickel. The name "Mercury" only refers to the dime and came into circulation in 1916. The "Mercury" dime was produced until 1945. In 1946 to present, it is called the "Roosevelt" dime.
Most likely this "doubling" is caused by erosion of the die, which happened often from striking these harder metal coins. Value a couple dollars.
"Counterfit is Death"
It's the Roman Numeral 5
Sorry, no US dimes were struck in 1991 with a V on the back
Back to Nature - 1911 was released on: USA: 8 August 1911
Paid Back - 1911 was released on: USA: 28 December 1911
Back to the Primitive - 1911 was released on: USA: 11 May 1911
Getting His Own Back - 1911 was released on: USA: 28 March 1911
Back to the Old Homestead - 1911 was released on: USA: 3 February 1911
The Cat Came Back - 1911 was released on: USA: 20 June 1911
The Man Who Came Back - 1911 was released on: USA: 20 October 1911
The Girl Back East - 1911 was released on: USA: 11 November 1911
Do you mean 5 centimes ? A 5 "francs" does not exist in 1911. 5 ct. 1911 : 15.386.000 coins were struck. Value : about 10 dollars in good condition.
It means the coin was not issued by the U.S. Mint and is just a copy having no monetary value.
it is on the back valve cover, you can't see it unless you remove the intake plenum.