I have never marked coins but see some marked coins here and there. I haven't counted them, but they are rare enough that it doesn't tell me much about whether my coins have been searched. The coin marks I've seen are generally a vertical black line on the obverse. I've also seen some black marking on the edges, but it's hard to tell if it was caused by a CRH. I'm marking my white and yellow string rolls with lines in black ink (I usually run the pen up and down the roll a few times), in case anyone comes across them. That said, I haven't deposited a lot of rolled halves, but that might change soon given problems with the coin machine at my bank.