The problem with this kind of debate is that the answer is usually fuzzy. In this case Nigel Bruce had many, many pipes.
A tobacco trade article from the 1940s states that of the five "notable" pipe collectors in Hollywood, Bruce ranked first. In case you're curious, the other four were John Ford, Archie Mayo, Jean Hersholt, and Arthur Hornblow (described as a less avid collector than Ford, Mayo, Hersholt and Bruce). Mayo and Hornblow, by the way, didn't smoke. The article goes on to say that compared to the others "...Bruce is the one who owns the largest number, all broken-in and fit for use. Nigel has bought and broken in an average of one pipe a week for the last ten years."
The article also states that "...during the filming of...
Suspicion...Bruce offered to use his own pipes. The deal [with Hitchcock] was made at 50 cents a pipe. Bruce used as many as ten different pipes in as many non-continuity scenes. But he drove the script girl crazy. She had to watch that Bruce didn't enter a room with one pipe and then leave it with another."
For the die-hards I suggest watching
Suspicion (always worth doing again) to see the ten pipes Bruce chose to bring from his collection to the set, out of the 500+ he's supposed to have had. For the less zealous, here's a photo taken on the set of
Suspicion with Cary Grant and Nigel Bruce, the latter with pipe in hand (not a bulldog in this case):