Don't believe I've ever seen a Baker side-by-side with a vent rib nor a Baker catalog listing for such.
Ithaca began offering a vent rib on doubles of No. 3 or higher grade with the introduction of the NID in 1926. I have seen both Flues & NID doubles factory retrofitted with vent ribs which have a ramp similar to Parker Bros. vent ribs.
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Parker Bros. is offering the vent rib on doubles in the 1927 pocket catalog, but the next earlier Parker Bros. catalog I have is 1923 which doesn't offer a vent rib for the doubles.
Fox first lists a vent rib for doubles in the 1931 Catalog and price lists.
Threaded Mode