This pattern is my personal favorite. Featuring two clip blades on opposing bolsters, in my opinion, it is the perfect every day carry knife. The thumb slits are on opposing sides, meaning you have quick and easy access to a blade no matter which direction the knife is facing when you pull it out of your pocket.
Pictured: Crandall Jig Cabernet Muskrat
The Muskrat is a double end jack knife and is sometimes also called a muskrat trapper. Interestingly enough, Case did not assign a pattern number for these knives, instead the word "MUSKRAT" is stamped directly onto the blade tang. In production, Case actually uses the same frame as the #47 pattern for the stockman.
Most muskrats made by Case measure 3 7/8″ when closed. However, there are a few smaller sized muskrats that were assembled on the #18 stockman pattern. These versions measure only 3 1/2″ when closed. Muskrat knives were introduced sometime before 1940.
Originally developed for the trapping trade, it gained popularity primarily in Muskrat trapping. It's quick access to a fresh, sharp clip blade when the other goes dull made this knife invaluable in the backcountry when working with hides.