Gold coin 20 francs portrait of napoleon III.Reverse side bays oureol with "A" on the bottom center 1855

Question

How much will cost if it is value

Answer 1

The "A" means the Paris mint.  Should weigh 6.4516 grams, and contains .1867 grams of gold.  They made 5,729,000 of them - too many for it to be "rare" or "scarce" for many years.

Approximate values - uncirculated $350.00; extra fine 200.00; very fine 175.00, fine - melt value (US dollars).

EDIT:  The coin linked by the other poster is actually a "BB" mint coin, which is the Strasbourg mint.  France has no "HB" mintmark.