If it was made in the UK, you should be able to find a "K" in there some where, it is usually 99K, or you will find the factory designation from the serial number. I can easily see why a UK made 99 has a US made motor, because of the Voltage differences beteween coutries (as I'm sure you are aware of) it would have been replaced. It could have been a hand crank and coverted to electrical motor too. I'm pretty sure all UK made 99 with original wiring will have two prong plugs. I think the last 99 was made in the very early 1960s, the first one about 1910 (before the three prong type). This model reponds very well to cleaning, oiling and a bit of care. It should run lightly and smoothly. Mine can get a bit noisy at full speed, I hardly ever push it to its' limits though. Make sure felt or rubber feet under the case are in good condition, check the belt too. If you are new to 99s; to take out the bobbin case fore cleaning, slide the bobbin cover completely off, there is a lift up lever there that slides towards you. This model turns very lighty when clean and oiled.
Last edited by Mickey2; 09-12-2020 at 05:01 AM.