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Believe it or not back 55 or so yrs ago I unloaded NEW JD model B drill components from a railroad box car & then got the "pleasure" of assembling the pieces into grain drills. I can't remember ever seeing in person a model B drill with wheels with bolt on cap. IIRC some sprockets have part # cast into sprockets
18 tooth sprocket I located is part number M10113 which is listed on JD's parts site @ $115. Hub cap is PN N160060 but not listed on JD Parts or Parts Depot search