What I will guess is that they tried doing it and then they didn't like it.
And why would they fill in the script with gold leaf on only one gun?
Evidently you have a very unique or at least uncommon set.
Personally, how do you feel about what the script looks like in that set done either way compared to the sets that have a plain barrel without any "commemorative" script?
Which do you like the best, the plain barrel, the gold script or the plain script?
There must be a reason why they didn't do it on all of them.
Maybe someone in management made the final decision and that was that.
And now you're the lucky owner of the set.