The training set used contained 12,612 images from two U.S. hospitals. Training set had a maximum age of 228 months (19 years), mininimum age of 1 month, mean age of 127 months (10 years 7 months) and a standard deviation of 42 months (3 years 6 months). See more details here.
 Cree M. Gaskin, MD MBA S. Lowell Kahn, J. Christoper Bertozzi, Paul M. Bunch. Skeletal Development of the Hand and Wrist: A Radiographic Atlas and Digital Bone Age Companion. Oxford University Press, Feb 1, 2011. (Adapted from Greulich WW, Pyle SI. Radiographic atlas of skeletal development of the hand and wrist. 2nd ed. Stanford, Calif: Stanford University Press, 1959.)