These dealers are the older, more established ones that have been in business for decades :
1. Monetarium (S) PL #02-34 The Adelphi
2, United Numismatic Center, Grd Fl Lucky Plaza
3. House of Collectibles #03-01 People's Park Center
4. Clifford Numismatic & Collectible Centre #02-45 Peninsula Plaza
5. Golden Million Coin & Currency Agency #02-07 The Arcade
6. Teck Kee Coins #B1-76 Golden Mile Beach Road
Can google coin dealers for more... For reference, advisable to buy those yearly banknote & coin guidebooks for S'pore/Malaysia, Hong Kong, even the International version depending on what you are collecting. Can attend the Spink auctions too. One local website for Singapore banknotes http://sgbanknotes.blogspot.com/p/buy-sell.html
I've have a stash like that, but it is of Singapore currency
I'm looking out for the Singapore $10 silver coins, $1 dollar lion coin, and the first/second series of singapore notes (especially the $25 note). I may look at the canadian maples, american liberties, lunar coins or the kennedy halves in the future.
for those who know about coin collecting, circulated coins and notes are usually not worth more than their face value years down the road. so, do not waste your time and effort on collecting such items. be in the know. read up about coin collecting first.
If your interested in going into silver coins collection, your might want to consider to purchase one "World Coins" By Chester L. Krause and Clifford Mishler which provide you details like pictures of the coins, weight, composition of the coin (example: weight of the gold, silver if any) and current market value for the coins conditions/grading.