Tailgate looks different

[Canadian 72 C15]

Just found an original stamped tailgate for my 72 GMC fleetside but part of the stamping looks a little different on the inside. I was told it was from a 68. I don’t think it should matter but you tell me or answer why it is. The stamped line at the top of this picture has a break in it for approx 4”. My tailgate now has that line solid from bottom to top of the gate. Any ideas ? See pic below. The second picture is to just show you the gate. Pretty good shape I’d say for its age and being a Canadian gate! Got it for $200cdn