They are standard. I tried a few years ago to order a 5 through a dealer, without thumb notches. No luck.
Now to contradict myself, I have at least two 5's without thumb notches. Perry told me that this happened once in a while to older 5's. I don't know if they were ordered that way or it just happened.
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Rod Brown RKS 3846 RKCC CM-123 Whether you think you can or can not, you are right.