For Duane -- Yes, I'm 99% sure that your 7 17 393430 represents a Jul 1917 393430 body number.
For Ryan -- Zooming in I agree that the first visible number is a 4 (see below). Some of the other numbers are hard to know for sure -- but not critical -- as so far none of them appear to be the date code for the body.
For both Duane and Ryan -- please look at the heel panel (both front and rear seats if a touring) and see if there is a letter stamped into the panel. If there is which letter is it? (Where to look? Please see below).
For all -- Beaudett & Fisher both put the year and month in their body serial numbers in the late 1917 to 1918 time frame (I have at least one documented samples of each of those). Beaudett put the month and year in the body numbers as well as the letter B for many years until Ford USA stopped purchasing bodies from them. In the very early years (1908 Model S -- they did NOT include a date in the body number -- not sure when that started. For the 1915-16 time frame Beaudett used a metal tag on the wooden front seat frame). Wilson also put a date code at least at the end of 1915 time frame.
Please see the Forum posting “Home for the Holidays” at:
http://www.mtfca.com/discus/messages/29/40322.html for photos and details on where to look and what to look for.
Note, so far I have not been able to make a great correlation between the body number and the year of the car etc. I haven't gotten enough samples to figure that out yet -- or there may not be a real correlation? Any way -- in about a year and half I plan to start working this research more -- as I hope to retire from my day job? So is the body number important? We it was back in the mid teens. Ford USA put out the following factory letter:
JUN 26, 1915 Factory Letter
"Hereafter when ordering body panels for 1915 cars, please give both the car and body numbers. The body number will be found on the right sill just inside the front door. This number will be preceded by a letter which indicates by whom the body was made.
"The above information is necessary as panels for bodies made by our various suppliers vary somewhat."
ref:
https://www.mtfca.com/encyclo/doc15.htm
But for registration of the car the body number is not critical. You can also use other items to help figure out the approximate date range of a body. Especially if the car appears to be mostly original. I.e. is the engine serial number related to the car or do you know it was replaced (many were and many still are being replaced). Is the body original to the car? Does the body have most of the original parts or do you know it was made up from parts from several bodies? (If I get my 1915 cut off called Blackie put back as a touring car -- the front half is 1915 and the back half will probably be a 1917-20ish as that is the oldest back half I have found so far that I could afford etc.)
It can be fun to help figure out what likely happened to your car over the ages. Sometimes you can only guess. Other times you can find "fossil evidence" of what was done in the past. And a few very fortunate people have a car with a documented since new history.
I hope the link is of some help to you. And if anyone has additional body numbers -- I would love to collect that data for a future possible article?
Respectfully submitted,
Hap l9l5 cut off