I'm not sure this is what you are talking about but this is "A Dovetail Joint Puzzle"
The Boy Mechanic: Volume 1, by Popular Mechanics way back in 1916.
"A simple but very ingenious example in joinery is illustrated. In the finished piece,
Fig. 1, the dovetail appears on each side of the square stick of wood, the illustration, of course, shows only two sides, the other two are identical. The joint is separable and each part is solid and of one piece. In making, take two pieces of wood, preferably of contrasting colors, such as cherry and walnut or mahogany and boxwood, about 1-1/2 in. square and of any length desired. Cut the dovetail on one end of each stick as shown in Fig. 2, drive together and then plane off the triangular corners marked A. The end of each piece after the dovetails are cut appear as shown in Fig. 3, the lines marking the path of the dovetail through the stick." See attachment for more details