gil;
Not sure what slot you are referring to. Only slot I see is the slot in screw head of lock plate screw. The cocking indicators are round pins which protrude when gun is cocked. The indicators in these views can be seen either in or just above the oval in engraving scenes, above the dogs. In one view the upper edge of the oval incorporates the indicator pin. On some is just above & on others inside, depending upon size of the oval.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra