Digital BW, The Print

Technically, Sharpie markers are not archival-grade.  The Stanford web 
site (Sharpie FAQ) makes that statement.  I had several labels in black 
Sharpie on archival-grade paper, and the ink had developed a yellow halo. 
  Your mileage may vary.

-Jon Dubovsky

Walter Scott Martin wrote:
> Carl we in the industry use a pen that goes by the name of Sharpee.  
> A photographers best tool it will easily remain permanent on the 
> surface of any coating, and will not leave a heavy indentation in the 
> surface of the print.  They come in three main widths.  The smallest 
> of the three is what you are looking for.  Good Luck
> Walter Scott Martin