Once again, very easy to remember, the early, first frames A-54 standard auto or MK I, the left grip panel, the bottom hole is closer to the bottom of the frame, the right side this lower hole is a bit higher, they reversed this pattern with the A-100 exactly the opposite, so from across the aisle, or table , without even picking up the gun to SEE or remove the grip panels to try and read a 'part number' (A-100) you can tell what frame is on that gun, cannot say this is "always" , better to say "normally" as folk have been swapping out frames since the beginning of the models......but the hole pattern tells the tale of what THAT frame is and what those grips will fit if you see a loose pair of grips sitting on a table.....
the hole pattern carried over to the MK IIs BUT the MK II "normally" has a hold open lever and the left panel is "notched" at the top , to clear this lever,,,yes, the MK II grips will fit the MK I A-100 frame but you have to put a "spacer" ( filler) in this cutout at the top of the left panel to keep the 'pin' in the grip frame in place...the Ruger .22 semi auto MK I, MK II,etc., grips when ON the guns, keep the frame pins "in place"........
