Technical Early ford transmission identification

Hi guys!
Can somebody help me for identifying my transmission?
I'm a bit confused, and I have to check what can reasonably be done to rebuild it or think about replacing the entire trans.
The number stamped on the top of the case is a "18-" code, the one at the rear is 78-7006-? (I can't read the last letter due to the crossmember proximity).
As per vanpelt page I can reasonably believe that is a type B or C case due to the rib on the bottom.
Please find attaches pictures, hope you can help me.

 

It’s a 1939 serial number.

I highly recommend VanPelts for the excellent book on rebuilding, and any parts you might need to do the job.

 

Thank for this prompt reply.
So it is finaly what I bought it for !

 

Yes 1939 ford V8 85hp 18-4,661,001 to 18-5,210,700

Serial numbers are available on Mac Van Pelt's site. Very useful.

http://www.vanpeltsales.com/FH_web/flathead_serialnumbers.htm

 

Looks like something got caught in the gear teeth of the main drive gear….the image shows some heavy damage to the gear teeth. There may also be some corresponding damage to the big end of the cluster gear. I can’t see the 2nd gear synchro ring, but the 3rd gear ring is just about totally worn out. The complete transmission should be torn down and inspected. A full rebuild should be in its future.