You'll need a microscope to get a good look inside to tell if it's multi-chip or single-chip.

Have a pic of a 1w Nichia 460nm emitter, multi-chip, and an Osram 660nm single-chip emitter. Note the bonding wires inside of each die area and where they connect. Some single-die emitters use multiple bonding wires for better electrical saturation of the diode, but it should be fairly easy to tell if it's single or multi.