If it was double struck then the "\ /" and extra "delta" should match, which they don't. Could be overstruck on a different type, but which?
The extra "delta" really does look like a delta - very straight lines and sharp corner. The "\ /" would make a bit more sense as remnants of the liquid being poured from a patera, although given the positioning, it seems that'd have to come from an overstrike.
I'd have bought it as a curiosity, but I generally prefer coins that are typical rather than atypical, for potential illustrative purposes.