Mr. Watson is correct.
In his book titled Best Guns author Michael McIntosh had this to say on the subject:
"In 1921, Ithaca brought out the Lefever Nitro Special, a modest gun that sold for $29. It was a sturdy utility piece bearing the unmistakable mark of Ithaca design and had little in common with its predecessors aside from the Lefever name. Serial numbers began at 100000.
"It may not have been beautiful, but the Nitro Special was tough. Factory records refer to it as the first gun Ithaca designed specifically for modern ammunition, and an advertising flyer dated February 15, 1922, says that the first lock was dry-fired more than 77,000 times and the first gun fired some 100,000 times without any malfunctions...
"The earliest Nitro Specials were available in 12, 16, and 20 gauges. In 12-gauge there was a choice of 28- or 30-inch barrels; the others were 28 inches only. The right barrel could be bored modified or cylinder and the left modified or full. The black walnut stocks were of industry-standard dimensions with no special factory alterations available."
According to author McIntosh, the Nitro Special went out of production in 1948 along with all the rest of Ithaca's doubles.
Hope this helps.
Good luck, and good shooting!