AH479497 is the serial number. The machine has slightly concave bobbins and it DOES have the slide plate.
It didn't have the power cord, but the foot control is there. I have a power cord from a 15-91 so that's no problem. Can't sew on both at the same time anyway!
Poor baby is bone dry. I went ahead and bought it, the table is in wonderful condition. The bobbin area is different from any machine I've seen, very interesting! It's calling to me so I need to get off this computer! I'll hunt down a manual when I figure out which machine it is.
Thanks for the info Joe, narrowing it down to the 66 helps me head in the right direction.