Company sees revenue spike at US$65.7m in last six months of 2013.
US, China and Japan become key markets for De Beers diamond brand.
Diamonds from Letseng mine will be sold at company's February tender.
Reports to use exclusive GIA paper and QR codes from January 1.
Bonhams bags $8.2m for pear-shaped diamond weighing almost 18 carats.
Facility to lead dedicated research in historical pearling nation.
Retailer seeks efficient, reliable and consistent supply of diamonds.