We just bought a New Idea one row picker and don't know what number it is. The only thing I can tell you is that it has wood on the bottom of the ear elevator going up to the wagon. I cannot find a tag or number on it.
The first thing is to look at the back of the picker behind the snapping rolls. Look for an adjusting lever that changes the opening/distance between the rolls. If there is no adjustment there and there are 6 steel husking rolls, it is a No 7; made somewhere between 1945 and 1956. In about '56 they started making the No 10 with a snapping roll adjuster at the back. All later models had that. In about '62 they started making the 310.
In about 1965, they started producing the 323 as part of their "Super-Picker" line It was considered to be the best they ever made; greatest capacity, least shelled corn (they said). These pickers usually bring much more money than a 2 row of equal vintage. The earlier pickers had steel paddle wheels over the steel husking rolls. The 323s had the rubber finger wheels over the 6 rolls, half of which were tire-carcass rubber rolls. The earliest pickers, while doing a clean job of husking, left a lot of shelled corn in the field. Hence the last version is the best/priciest/greatest capacity. The earliest models had the wood on the elevator with steel paddles. The latest had no wood and rubber paddles instead.