Don - That is an interesting stamp. The "DISP." could possibly be short for Dispensary, which is a chemist or druggist in old China. I found a picture postcard on eBay
showing a street scene in Tsingtau, which I scanned below. Notice the store sign on the left side of the picture for Ling Dispensary - Chemists and Druggists.
Your stamp could be for Lee Man Chung Dispensary and could be some sort of seal used in their business. I will look some more, but this may be a clue to the mystery.
Also, the design in the center of your stamp is in the shape of a heart.