Vajra (thunderbolt) is the weapon of the King of the "lesser" Gods - Indra, which is also the guardian of the Budhism.

In Hinduism, Shiva the Destroyer has 2 sons - one of them is Skanda who's actually an image of Alexander the Great who used the lance which is an epiphany of Vajra. Skanda is the Hindu version of Narayana. BTW, Narayana is also known as Weito. There is a grass root Daoist version of Narayana (I should say Skanda) which is Nuo Jia the Third Prince. Weito together with the 4 Heavenly Kings (Si Da Tian Wang) makes up the guardian force of Chinese Buddhism.

So in the posture with the hand that holds above the head represents holding a lance/Vajra and ready to throw it.

Just a thought

Mantis108