Q. I'm looking for a used piano to buy and found white marks on the tuning pins. Does this mean anything?

A. Yes.  Many piano techs will mark tuning pins that do not feel tight with chalk or some other white mark.  This could be a cause for concern as the piano may not hold tune well, or for long, or possibly those pins will not hold tune at all.   There are 4 tuning pins in the bass section that I have marked on this piano.  These are tight enough to hold pitch but loose enough to make them very 'touchy' when tuning and they are always the first strings to go out of tune.  Sooner or later they will not hold at all.  This piano is a good candidate for pin block treatment. (see question about why a piano may not hold tune.)