White Speedylock Differential 1600 White Speedylock Model 1600 was made sometime between 2003 and 2007 Functions as designed .light works also

"White Speedylock Model 1600 Overview"

The White Speedylock Model 1600 looks pretty much like all the other sergers manufactured at the time with one glaring exception. There is a huge dial on the left side of the machine that controls the differential feed. The markings on the dial clearly shows how easy it is to select the settings for stitch narrowing and widening or to handle sewing curves of any size or angle and to make fancy edges for tops, dresses and skirts. When you open the looper door, you will see an uncomplicated, easy to follow threading path No Delivery Local Pickup Live in City of Roy