Using the simplest brand of numerology, that of converting numbers to letters, the numbers 9 and 22 translate out into I and V.
So you have to ask yourself, if the devil wanted to mark the age of his power (1941-1980) that he had been given by God as a result of asking for and receiving Romans 9:22 style Objects of Wrath and Destruction, where and how would he display an I and a V.
Someplace presumably where not everyone would be able to spot it. 
Aside from in actuality being an occult symbol, the peace symbol was also used as a Nazi death symbol. 
Cool 