“The Model K reproducer was the first Edison reproducer to incorporate both a 2-minute and a 4-minute stylus on a single reproducer. While still retaining the same body and weight shape as the Model C and Model H reproducers, the tail weight was of a new design. The central portion of the weight was able to swivel 180 degrees so that the correct stylus could be brought into use. Originally supplied with the combination Fireside and combination Gem phonographs only. Combination Standards, Homes &: Triumphs were still supplied with both the Model C and Model H reproducer. The short coming to this reproducer was that to change from a 2-minute record to a 4-minute record, the reproducer had to be removed from the phonograph so that the central part of the weight could be rotated to the correct position.”
the different types and more info: