The old Forgotten Realms Adventures hardback from 1990 had a fairly extensive chapter on treasure in the Realms, and ways to make treasure (coins, gems and art objects) Realms-specific. I always throw lots of these into my Realms games to add flavor.
Here are alternate names for coins, and alternate coins:
Platinum:
Tricrown (generic name for a platinum piece)
Amnian Roldon
Gold:
Cormyrian Golden Lions (the de facto standard gold piece, a 5-sided coin)
Amnite Danter (common in the south)
Tethyriian Gulder moelan, myrat and zoth
Silver:
Cormyrian Falcons
Sembian Hawks (the coins are triangular)
Amnian Tarite
Calimshite Decarche, Espedrille and Red Worm of Memnon (a silver piece with thin layer of ochre paint, ones with the dye worn off are commonly called "skinned worms")
Copper:
Cormyrian Thumbs
Calimshite Unarches, Rada, Niftens and Spanners
Amnian Fanders
Electrum Pieces: (Not in common use in 3e, but in earlier editions they were worth half a gold).
Cormyrian Eyes
Sembian Electrums (Diamond shaped)
Calimshite Tazos and Zonths
Amnite Centaurs
Silverymoon Moons (worth 1 ep normally, worth twice that, essentially worth 1 gp, in Silverymoon)
Other:
Steelpence (Steel piece worth 1 cp in Sembia)
Bela (paper money from Kara Tur, sometimes used by the Hordelands barbarians, essentially worthless in the Realms, sometimes given as an insult.)
Blood Notes (IOU's and promisory notes)
Mirabar Trade Bar (rectangular black iron trade bars worth 10 GP in Mirabar, 5 GP everywhere else)
Merchant's Trade Bar (bullion bars of gold used as high-denomination trade, minted only by merchantile institutions, not by countries. Come in 10 gp, 20 gp and 50 gp denominations)
Sembian Trade Bar (bullion silver bars minted by Sembia as high denomination trade bars, in 5 gp, 10 gp, 25 gp and 50 gp value)
Lantan Trade Bar (flat, envelope shaped trade bar of steel with the holy symbol of Gond stamped in, worth 20 gp in Lantan and on the Sword Coast [where Gond and the Lantanese are often found] practically worthless elsewhere.
Waterdeep Toal (square brass coin with a hole in the middle, worth 1/2 of a gp in Waterdeep, virtually worthless elsewhere).
Watderdeep Harbor Moon (Small platinum coin with electrum inset, worth 50 gp in Waterdeep, 2 gp everywhere else)
Shou Lung Copper/Silver (generic term for a copper or silver piece that is unrecognizable in nature but still made of copper and valuable as raw metal. Rarely comes actually from Shou Lung, but it's a common term for it.)
Shou Lung Trade Bars (long slender bars of silver stamped with oriental symbols, worth 40 gp)
Letters of Trade (Letters tradable on demand for a specific item, ones found as treasure are still only valid about 10% of the time, sort of an IOU for a non-monetary item).
Tharsult Statues (Small statuettes of ivory and jade used as trade items in Tharsult). Worth 15 gp as an art object and curiousity in most of the realms, worth only 5 gp as a trade item in their homeland.
Shaar Rings (bundles of rings/discs made of ivory and hung on long strings, used as currency by natives of the Shaar. A typical ring will be worth 3 gp for the Ivory in it).
Gond Bells (brass ornamental bells enclosing an ornamental stone, worth 10 gp on the open market, 20 gp in trade to the Church of Gond)
Mercenary Cards (pay vouchers from mercenary units, typically the size of a playing card, signed by the unit's paymaster, typically with a seal or insignia on it).
