Coin Collector Warehouse Keeper Sorint asks you to meet with Hunters Union President Bernard and retrieve the golden dragon of Kaldis.

Bernard's coin is a family heirloom and you can't have it. You might find something similar, however, since the Mystic who gave it to us was ultimately killed by lizardman in the Forest of Mirrors..?

Monsters to Hunt - Harit Lizardman Shaman, Harit Lizardman Chief

You've obtained Kaldis's gold dragon coin. Take it to Warehouse Keeper Sorint.

Sorint accepts the coin and offers you a Coin Collector Membership Level 3 as a reward. Get the coins by hunting monsters. You can also trade low-grade coins with other Level 3 members. Ask Sorint for details.

You can find other level 3 coin collectors at the following locations:

Entrance to Cruma Tower: Researcher Lorain
the Town of Oren: Warehouse Keeper Hagger
Hunters Village: Magister Page

Ask Bernard what you should hunt to collect coins.

The following monsters are known to drop coins -

Hunters Valley: Lakins
Plains of Glory: Vanor Silenos Shaman
Timak Outpost: Timak Orcs
War-Torn Plains: Hatar Hanishees
Forest of Evil: Formors, Tarlk Bugbears
Outlaw Forest: Ol Mahums
Dragon Valley: Malruk Succubus Turens, Headless Knights, Royal Cave Servants, Shackles
The Cemetery: Tortured Undead
Killing Ground: Grave Lich, Doom Servant, Doom Archer, Doom Knight
Garden of Wild Beasts: Kookaburra, Antelope, Bandersnatch, Buffalo
Valley of Saints: Claws of Splendor, Wisdom of Splendor, Punishment of Splendor, Wailing of Splendor
An Old Battlefield: Hungered Corpse, Bloody Ghost, Nihil Invader, Dark Guard

Take any coins you collect to Warehouse Keeper Sorint.

To advance your membership level, you must obtain the following low-grade coins. Trade with other members for them and then take them to Sorint.

You've become a level 2 member of the Coin Collector's Club. You're now eligible for the level 2 premium and may trade with level 2 members.
Members who can be traded with at present:
Level 2 Member
the Town of Oren: Guard Stan
Hunters Village: Blacksmith Duning
Underground Shop

To become a Level 1 member, you must collect mid-grade coins. Take them to Sorint.

You've become a level 1 member of the Coin Collector's Club. You may now trade all premiums from Sorint and trade with all members.
Level 1 Members:
Aden Castle Town: Head Blacksmith Ferris
Giran Castle Town: Warehouse Keeper Collob
Floran Village: Grocer Pano