Our system is simple:
If piece of wood has no curl is straight grain; Grade 1.
If few curls are present, but they are not uniform or consistent is a Grade 2 or Grade 3 (The more curls, the higher grade).
If a piece of wood begins to show irregular curl in 50% to 60% (or a little more) of the total area of the piece trough out the full length, whether is more intense in one side or in both sides is a Grade 4.
A Grade 5 is the most difficult to grade, but basically one judgment that we often use is: if it is too good for a grade 4 because it offers abundant curl, considering uniformity and presence trough out both sides of the stock, yet the uniformity of the curl is not consistent to grade a stock as Grade 6... then it is just a Grade 5.
A Grade 6 offers the gun builder a piece of wood that begins to show a good balance of curl full length and in both sides, however, the level of boldness for the curls themselves is not superior.
A Grade 7 is a stock that gives you a sure bet and offers different levels within. Once it reaches the grade 7 level, the price is determined by the uniqueness of the figure/curl, grain alignment and boldness presentation of the figure.