About the NO model, I think it stands for Normal or something similar, meaning the classic 1950 shape and not the "improved" 1952 or GK with slanted bolt handle etc. I think that in the 1960s there was the GM, MC and NO models, where NO was very similar to the older 1950.

I used to have a full stock NO in .30-06 which is quite common here in Sweden.

/L