Kelly Kearse sends along another grid (you should probably first read Who took which sticky tape samples where and when? 6BD Pictured?):

Attached is a picture from an ’84 Shroud Spectrum article showing an earlier grid system developed by B. Bollone & A. Ghio. This numbering system appears different from the labeled magnet frame coordinates used by STURP in 1978. In the BG grid (Bollone-Ghio), the right cheek area looks like it would fall within 6Bd. Perhaps this grid was used by Frei (in 1973)?