While cleaning the firewall on the '48 F6, I uncovered this stencil 4-15-??
My guess is that its a date of manufacture. But the numbers stamped above the firewall decode to April 28 1948.

So....Any thoughts as to what it was?

 

I found a similar set of faded yellow numbers behind the gas tank in the cab of my 1949 F4. These numbers were in line with the date of manufacture.

 

My '49 F4 has a number like that stenciled on the bottom center of the firewall. Mine is 1-24-A, I understand that it means Jan 24 A shift.

 

^^^^^That makes sense, Thanks!