The gun was posted on shotgunworld.com and I certainly didn't know an answer, so I brought it over here. A lot more shotgun knowledge on the PGCA site than other boards around the internet. When it comes to Ithaca doubles I'm primarily an NID guy. From what I've observed Ithaca started their zero to four choke markings on the front of the barrel flats at about 200000 in the Flues era. Sometimes they marked the chokes as a fraction --
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but usually just the numerator --
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I haven't spent any time looking under the extractors/ejectors of earlier Ithaca doubles, so don't know if others have numbers stamped there. I kind of like the idea of Remington like pellet count but taking the extractor out and stamping a number after you've fired the gun and counted the pattern seems pretty labor intensive.