I saw this ad on craigslist so I emailed the seller for pictures.
http://newyork.craigslist.org/brk/atq/4183137695.html
The serial number is G209230. The (very nice) seller even cleaned and polished the plaque to be sure she read the number correctly. According to ISMACS, it is one of 30,000 numbers allocated on Jan 8, 1910. The next allocation of serial numbers for model 66 was March 16, 1910. The next after that is June 22, 1910. There are patent dates on the slide plate, and the last one is June 14, 1910. So, either the slide plate was replaced or Singer allocated serial numbers as far as two or three allocation dates in advance of manufacture.
[ATTACH=CONFIG]446760[/ATTACH]
[ATTACH=CONFIG]446751[/ATTACH][ATTACH=CONFIG]446752[/ATTACH]
[ATTACH=CONFIG]446750[/ATTACH]
There are some other interesting things about this machine. At some point the presser bar was changed from back-clamping to side-clamping, and the handwheel was changed out, I assume when it was electrified. But it has no motor boss, so where would the motor have been mounted? It has one of those funny controllers. I've seen them in pictures but not in the wild (as Tammi would say).
I just noticed something else. Do I see light coming thru the rear inspection hole?