Sherry gene: sh.
The mutation is so detrimental, it won't be found in any OP cultivar for sure.
It is a mutant of the variety 'Canary Export' by ionizing radiation.
Plant is "extremely unfruitful". details here:
http://tgc.ifas.ufl.edu/Vol30/Vol30/Vol30_26.html
http://forums.seedsavers.org/showthread.php?t=552