Chris,
I think John Hinckley had the correct answer. The wacky characters were obviously stamped BEFORE the cyl head was installed because even individual character stamps wouldn't have been able to place the impression that far aft with the head in place. A VIN stamp, if applicable, would have been applied at the point of vehicle assy just before installation in the chassis so the engine would have been complete with heads installed.
I think John Hinckley had the correct answer. The wacky characters were obviously stamped BEFORE the cyl head was installed because even individual character stamps wouldn't have been able to place the impression that far aft with the head in place. A VIN stamp, if applicable, would have been applied at the point of vehicle assy just before installation in the chassis so the engine would have been complete with heads installed.