The quality control at Parker Bros. was beyond reproach. I don't believe anybody at PB was trying to deceive anyone or cover up a mistake.... but never say never... The original owner of that gun, in private correspondence with King, may have agreed to the change in barrels... we'll never know.
I sure would like to see the barrel steel letter stamp on the right barrel flat

There is a "
K" in the location for the barrel steel and
K is not the designation of any PB barrel steel... As we know,
K is Charles King's stamp of approval.
That rib just doesn't look like anything PB would have let out of their shop.
Just my HO