Almost every handyman-around-the-house knows "Plumb" hammers and hatchets. Philadelphia's venerable Fayette R. Plumb, Inc. has been making fine tools since the 1880's, and is proud—and jealous—of its trademark. Not so well known is Los Angeles' Plomb Tool Co. (named after Alphonse Plomb, one of three founders), a much younger firm (founded in 1907). When Plomb applied in 1926 to make its name a trademark, Plumb promptly squawked in court. The result was a deal in which Plomb agreed not to use its name on anything that resembled the famed Plumb Tools.
But Plomb did not keep its word, and, after...