Thought it may be useful to all [Singapore].
I was talking to a friend whom was working at Seiko AD (Thong Sia) previously.
This is how they distinguish Seiko Local Authorized Dealer (Thong Sia’s agent) and gray import warranty card (see below).
Warranty card with the prefix of “521” in the warranty card denote Seiko Local Authorized Dealer (Thong Sia’s agent).
Japan Domestic Model (JDM) has a prefix of “899” in the warranty card. To make a claim, the warranty card MUST be stamped.
*those with Seiko International Warranty (JDM) should still be valid outside Japan but repair and claims will have to be done in Japan (send back to Japan!).
Other prefix are consider self import, grey market, parallel import. Warranty claim may not be applicable.
*this may defer from country to country local AD policies.
Please do add more details, if any………….
seikoparts 
521S1 – Area code for Singapore
520S1 – Area code for Hong Kong
899SA – Area code for Japan
578S1 – Area code for another country, but it doesn’t means that is come from Grey Dealer