Confidence: Smith & Green Jewellers offers high standard of member staff and information to make sure every couple feels confident in what there are buying. Certificates: We are very strict on the range of Certificates we work with. There are three certificates we recommend, GIA, HRD and IGI. GIA (Gemalogical Institute of America) Certificated Diamonds but also HRD (Hoge Raad voor Diamant) and IGI (International Gemological Institute) Certificated Diamonds.