Larry is right that Ithaca dropped their Deeley forearm latch on the extractor guns, and replaced it with a Baker J-spring, when they introduced the New Ithaca Field Grade circa 1935.
They also changed the ejector gun forearm fastening from the opposing Deeley hooks to a Baker J-Spring locked in place by a lever actuated tilting block, similar to the Parker Bros. forearm latch.
1933 above, 1936 below. Ithaca also went to a much nicer looking, longer, beavertail circa 1935. Also about that time they dropped the Grades No. 1 and No. 3. A handful of No. 1 exist with the new features --
This No. 1, 28-gauge, has the J-spring forearm and no cocking indicators, and according to Walter was shipped in late 1935. I've seen and handled a similar Magnum-Ten.