Grade 1 guns I, K, L, M, N, O. P, Q

[jeffery c]

What are the differences between the letter grades in grade 1 hammer guns? I have one enroute that has laminated barrels, does that fact decide which letter grade it is within the numerical grade 1 group? On the homepage on the Parker Grades section it says, "As Parker introduced the named grades they named Grade 1 guns I, K, L, M, N, O. P, Q, NH and PH." The pictures linked to at the tab on the bottom of the page states that grade 1 is the same as P grade in toplever guns. My gun is a grade 1 but my question is how do the letter grades I-Q fit in or does this gun fit into the letter scheme at all, being an 1888 gun?