Up until 1953 they also didn't have the model number shown, but after this Singer added a riveted plate with the model number just below the badge. These were all produced at the Kilbowie plant in Scotland.
The K7's were white and quite plain with no decoration except for the Singer name on the lamp cover in gold decals.
Early 221’s had a tray in the top which rested across the top of the machine and housed the attachments and the power cable and foot controller.
Trying to squash the stiff cabling into this narrow area proved difficult so later machines adopted the system also used in the 222’s case.
If you have one and would like to know the date that it was manufactured just out of curiosity or if you are trying to fix the machine, you can do so with the serial number.