Featherweights have several distinctive features. The first is their size and weight. A featherweight isn't that much larger than a child's machine and only weighs 11 lbs. It is usually black but a few tan ones were built in Canada and some of the latest models were white. A featherweight will only sew forwards and backwards. There are no other stitches. The bed of the machine has a flip up part that is used in the up position to access the bobbin or to pack it away in the small rectangular black case. Some featherweights came with cabinets (extremely rare or folding card tables) If you Google featherweight or Singer 221 you'll see some pictures of the machine and distinctive case. The shiny metal faceplate may have a striped pattern (striated) or a more elaborate Egyptian scroll plate. Featherweights were made from the 1930's until about 1970 and small changes occurred during those years. The light switch may be on the light or on the base in the bottom right corner. Earlier featherweights had plain silver feed dog plates while ones from the 50's may have the seam line marked on the plate. The bobbin case (make sure the machine has it as it is expensive to replace)is round with a little spring loaded lever used to insert it and the bobbin is narrower and flatter than a class 66 bobbin. The electrical cords attach to a plug and are removable for storage and the original food pedal has two buttons of which only one can be depressed. Only white featherweights have electrical cords that were wired directly into the machine (cost cutting measure). The black case has distinctive suitcase looking locking hinges and has a tray (various styles) to hold the attachments. The number 221 does not appear on the front of my machine.