Complex sentence: Generally, artifacts of this kind are not altered because of their historical significance; however, Deo Fisher in 1992 the emerald was cut down to 12.72 carats, making it one of the largest and the only named cut emerald from the "Atocha".
Split into simpler sentences: Generally, artifacts of this kind are not altered because of their historical significance. In 1992 the emerald was cut down to 12.72 carats, making it one of the largest and the only named cut emerald from the "Atocha".