Bottom is a very early 1919 NRA with the first size ejection port.

Middle is a 1922 Sporter with a slighty more open port - the 1919 NRA's also went to this - if you look close it's only the surrounding metal that got releived, the top of the actual opening is flat - the height of the ejection port is still the same as the early one = the height of the bolt nose.

Top is a 23-A Sporter - udated bolt and much larger ejection port, the NRA got the same update in 1923. To tell them apart look at the knob on the rear of the bolt, the actual shape of the ejection port openin, not the shape of the releived metal around it, and where the top of the bolt handle is - in the 1923 version it is below the top of the stock and the stock has a bigger relief.

[Linked Image]