Stellazzios

Throughout the game you will come across a variety of coins called Stellazzios, with each one being named after a star sign and a extra 13th one. With these coins you can gain various items by trading them with an aristocrat in Treno.

Which each Stellazio coin you give to Queen Stella in Treno she'll give you a reward. Here is the list in order.

 - 1,000 Gil
 - Pheonix Pinion
 - 2,000 Gil
 - Blood Sword
 - 5,000 Gil
 - Elixer
 - 10,000 Gil
 - Black Belt
 - 20,000 Gil
 - Rosetta's Ring
 - 30,000 Gil
 - Robe of Lords

After giving her 12 coins, she'll return them to you and ask that you use them as hints to find the last Stellazio coin, the Ophiuchus. After collecting all 13 Stellazio coins, give them back and you'll recieve the Hammer.

Below are their locations

Aries
Location
1st floor of the windmill house in Dali

Taurus
Location
Behind the item shop in Treno

Gemini
Location
Throw 13 coins into the fountain in Treno

Cancer
Location
Past the gate in Burmecia behind a wooden box

Leo
Location
Check the spiral stair case in Alexandria castle

Virgo
Location
The Inn at the Black Mage village

Libra
Location
Behind the fountain in Madain Sari

Scorpio
Location
By the spring in Quan's cave

Sagittarius
Location
Hidden in the commercial district of Lindblum

Capricorn
Location
Down the right water path at the start of Daguerreo

Aquarius
Location
In a chest at the side of the first hall in Ipsen Castle

Pisces
Location
Check the chest at the centre of the ship Invincible

Ophiuchus
Location
In the same place as Scorpio