Not enough information. On a bill, it might be a Federal Reserve indicator, a series letter, or part of a plate number depending on where it's located. On a coin, it might be part of the designer's monogram.
If you have a specific example or examples, please post a new question with more details such as location, nearby text or images, etc. so a more specific answer can be provided.
In Europe, a belciqve 20 f coin is worth approximately $20.00 USD. However, currency changes daily, therefore, it is best to receive a quote from a coin collector.
The US has never used an "F" mint mark. What you're seeing is almost certainly the designer's monogram. In particular, Indian Head nickels have a prominent "F" for the artist James E. Fraser.
Please don't assume that every old bill is a silver certificate. The banner across its top and the red seal indicate it's a United States Note, a form of paper money issued directly by the Federal government. US Notes were discontinued in the 1960s. There's more information at the question "What is the value of a 1928 F US 5 dollar bill with a red seal?"
The "F" found beneath the date on the 1 oz. American Buffalo Gold Bullion coin is not a mint mark. It is the first letter of the designer's last name, James Earle Fraser.
Your bill would have been printed with a red seal but it probably faded due to age or exposure to light or chemicals. Seal colors were standardized in 1928; red was used for all US Notes Please see the Related Question for more information.
No US coin bears an "F" mint mark
The 35th President of the US, John F. Kennedy, is on the half dollar coin
The 50 cent coin bears the head of President John F. Kennedy
This is the designers initial.
You may be seeing an intertwined A and F on the coin's front. That's the monogram of the coin's designer, Anthony (Antonio) de Francisci, which is below Miss Liberty's neck on the coin's obverse. An "L" in any other place was probably added after the coin left the mint.
Belgium now uses the Euro, the I F is no longer legal tender and thus not worth anything.
If its a lead sheet symbol, your supposed to play an F major chord (FAC). Otherwise, its probably just the note F natural.
It could mean many things. F is also a letter place holder for a note on the violin. Ex: F can be 2 on D.
A 9 note is the equivalent to a B in the US. A 5 equals a F (fail) note.
thereisf sharp, f flat(note e), and f natural
The III note is A. However, the 3rd note in the chord is the V note. That is C. The F major chord is F, A, C.
I'm not sure how to explain this in words, but I play it as:Bb (half note), Db (half note), Db (quarter note), two quarter note Eb's, (quarter rest), Gb (eighth note), F (eighth note), Gb (eighth note), F (eighth note), Gb (eighth note), F(eighth note), Db (quarter note), Db (quarter note), Eb (quarter note) and Eb (half note).Repeat if desired.Hope that helps?