The prototype of this Buddha derives from the non-Chinese Tuoba clan of the Xianbei people who established the Northern Wei dynasty in northern geographic China. An example of a Northern Wei prototype, dated to 524, can be found at the Metropolitan Museum of Art, shown below. An Eastern Wei Buddha (image), dated to 536, is at the University of Pennsylvania Museum. Both images show the strong influence of the Northern Wei and its derivative dynasties on Korean art. Most images inscribed with a date during this period of history used the sexagenary cyle system; dates can be interpreted in more than one way by adding or subtracting sixty-year cycles to the inscribed year. Scholars must date images based on the context provided by other images. For example, the Yŏn'ga Buddha is generally accepted to date to 539 because of contemporaneous images from the Metropolitan Museum of Art and the University of Pennsylvania Museum, discussed above, which date to around that time, 524 and 536 respectively. 60 years before 539 would be a date too early for the Yon'ga Buddha while a date of 599 (adding sixty years) would make the image archaic and out of style.