According to paragraph 4, why did Holmes and Watson examine the walking stick closely?

"I have, at least, a well-polished, silver-plated coffee-pot in front of me"said he. "But, tell me, Watson what do you make of our visitor's stick? Since we have been so unfortunate as to miss him and have no notion of his errand, this accidental souvenir becomes of importance. Let me hear you reconstruct the mann by an examination of it."