This seems to have gotten thru quality control. Or maybe it's not that big of a deal. Is this a die chip? Common anomaly? Or a legitimate error? Sorry about the lighting. Thanks!
@TJ1952 I'm not sure what may have caused this although a "plating bubble" as suggested by @furryfrog02 is not too far out of the question. Yes, sometimes mistakes do get overlooked on proof coins like the 2005-S KS SQ Silver Proof, FS-901 which has a die dent visible to the naked eye. I'm guessing that the QC function is combined with the packaging function by Mint employees rather than an inspection by a separate employee. Chris