68 BB AC Clip Mounting

[big iron]

Looking at the 68 AIM C60 D5. The clip #8 is mounted to the bracket with #3,#4,#5,and #6. The bolt #3 and l washer #4 go through a threaded 5/16-24 hole just below the hole shown, then the clip #8,  l washer #5 and finely the nut #6.
Now the question. Why do they show two different lock washers being used? Is this correct? 
Bob