Leland,
I don't know where your set came from - I.e.if it would have been viewed for sale or online previously. In any case I have seen for sure two other Pigeon grade 2 barrel sets with Damascus/ fluid barrel options.
I suspect as Drew mentioned, especially with the higher grade guns, it was relatively common to return them for fluid steel barrels in the 10s,20s, and maybe 30s ( perhaps less so with the depression on?). I think likely more rare than the replacement is the Damascus set staying with it for 100 years.