I actually looked up the revised number on the comprehensive site and it shows that SN G0 (not the letter O) 463379 was issued on Nov. 13, 1923, which probably means that the side clamping feet are original to the machine. There are 7 digit numbers under the G letter late in the use of that letter and that is where this unit fits.
http://ismacs.net/singer_sewing_mach...l-numbers.html