Original Presidium Gem Diamonds/gemstones Computer Gauge - New! (PGCG) A convenient digital gauge that measures actual gemstone dimensions and estimates gemstone weight and identity. Presidium Gem Computer Gauge measures the dimensions and estimates the weight of loose and mounted gemstones with precision, speed, and ease. After entering the weight and the measurements of a gemstone, PGCG narrows its identity by computing its S.G. value. With PGCGs computer interfacing, gemstone measurement records can be easily imported and printed. For more details please check the Product Description.