The American Dental Association (ADA) Specification No. 5 for Dental Casting Gold Alloys specifies :
The American Dental Association (ADA) Specification No.5 for Dental Casting Gold Alloys requires a minimum total gold-plus-platinum-metals content of 75 weight percent (wt%). 
Sturdevant operative dentistry 7th Edition, Page No:e94
Minimum total gold-plus-platinum-metals -75 (wt%)
Minimum total gold-plus-platinum-metals -25 (wt%)
Minimum total gold-plus-platinum-metals -55 (wt%)
Minimum total gold-plus-platinum-metals >75 (wt%)