No one has been able to answer that question and provide satisfactory evidence that their answer is factual, that I am aware of. My personal belief, because of the way I envision the manufacture of Fox guns taking place is, "No", they are weight "markers" that were for the unstruck barrels without ejectors/extractors. I do not believe the ejectors would have been fitted before the barrels were struck to their final weight, and fitted to the frame. I also believe that the numbers were there only to provide a reference to the builder(s), not to provide any information of sorts to the owner, or subsequent owners. If that were not the case, the lightweight barrel sets would have had the number replaced after they were filed off in striking.
JMO, of course.
SRH
Bingo! The ejector/extractor parts were serialized to each gun. They had to be fitted when the gun was built, so they would not have been included in the weight calculation of the rough barrels. I have seen the rough barrels - bought a couple sets, actually - and they had no ejector/extractor parts.
