This work is based on a 4th century AD bas-relief sculpture from Gandhara, an area in Pakistan located on the Silk Road, where eastern and western influences mixed.  The position of his hands indicates that he is preaching.  While this form usually refers to Gautama preaching his first sermon at Sarnath after his enlightenment, the sculpture from which this image is taken may be a depiction of Amitabha or Maitreya preaching to his assembly in his pure land.