granny64,
Just to jump in here with my two bits:
Serial number AG 853182 shows to be a 221-1. 1 of 10,000 allotted 10-25-46. There is a group of 66s indicated in serial #'s AG- 832846 to 847845 on 10-25-46 so maybe your 66 got stamped in the wrong number sequence. Just a thought.
Serial number AC 853182 shows to be a Mdl 66. 1 of 35,000 allotted November 9 - 1929.
Could you post a pic of the machine and a close up of the serial number??
Joe