I thought the HP 48GX models with the black LCDs first appeared with the Indonesian made models with serial numbers starting with ID. The following eBay ad indicates otherwise:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=180206838591&ssPageName=ADME:B:SS:US:1123
The photo of the front of the calculator doesn't look like a Singapore model since the font of the keys is of the newer design. However, the photo of the back of the calculator indicates a Singapore model (although the serial number on the calculator does not match the one listed on the ad).
The seller has 100% positive feedback.
Strange.