I think that threat theory may be very sound. I dug out some more of my flatware for the hotels and camps and came across 5 pickling forks.
4 are marked " Dohrco Gramercy" & 1 is marked "Victor S. Co. A1" followed by an I & S in boxes for International Silver Co.
Victor Silver Company was acquired by International Silver Co when Derby Silver Co. was bought out. International Silver used much of the back stock pre-stamped flatware and like items and just added an additional mark. That's why the one pickling fork gives indication to these two makers.
If you look Dohrmann Hotel Supply's Gramercy pattern matches Victor Silver Company's Norman pattern. See Photos below.
I have tried digging for patents on both of the patterns and come up short. What I am assuming based on this is that the design was not patented by either company & Yellowstone Park Co. was in need of more flatware for growing business and needed to have the same design/pattern for appearances.
They could have brought the design to the opposite company and requested a batch made at a cheaper/more cost effective price than the previous company had to offer or one of the two companies stopped manufacturing that pattern and the other picked up where the other one left off. Because Victor Silver Co & Dohrmann Hotel Supply don't give clear dates as to what was manufactured when it is hard to tell.
I thought at first perhaps Dohrmann Hotel Supply may have purchased flatware stock from Victor Silver Co. as they were growing in the early 1900's but I can't imagine that they wouldn't both stamp the flatware at that point.