I can't really see the sticker on the back...photo is too small and fuzzy. The DD (Distortion) should have "SH-6" on it (it will also have a "B" on it if it is a bridge model, or an "N" if it is a neck model). If you have a multimeter measure the resistance between the red and green wires and between the black and white wires. If it is a bridge DD, each pair of wires should read 8.2 - 8.4k ohms.
Also, I don't see the Seymour Duncan logo engraved/stamped into the baseplate.
That could be a "Duncan Designed" not a "Duncan" pup.