IHC drawing numbers start with D. If there is an F then it is proceeded by an IHC. There's a ton of F drawing numbers in the 5.3 range. They are as early as 5.2. In Duffs book, 5292300 has a heat lot of A 5 5 C with an F marked drawing number. In addition that that, I have looked at a few welded receivers and yours is not welded.
Last edited by dryheat; 11-18-2014 at 08:18.
If I should die before I wake...great,a little more sleep.