The C.C. Roberts Bait Company of Mosinee, Wisconsin, is the oldest continuous manufacturer of wood baits and is still making lures today. Maybe that is due in part to the fact that Roberts only made two lures for commercial use, the Mudpuppy and the Puppette. The Mudpuppy came in two lengths, 7" and 5-1/2". There are a fair amount of variations in the lengths of these lures due to the fact that in the early years, they were hand-carved.
The early versions of the Mudpuppy was cut down the middle, allowing the tail portion to rotate. Later versions were cut different, with the tail portion being only about 1/3 of the total length of the lure. Also, earlier verisons had flaired gills. The pictures above show the older version on the right with the newer version on the left.
The Mudpuppy had an unusual hook design in that when a fish was hooked, the treble released from the body of the lure and the lure floated away free from the line. This made it necessary to retrieve the lure after catching the fish (assuming you landed it!). During WWII, the company had problems obtaining treble hooks and made their own trebles by using a double hook and a single hook and wrapping them together with wire, then soldering into place.