This is the only Pickworth I've seen with a brown protoconch. 1.5mm. I've asked Le Renard and Bouchet to identify this if possible. They wrote "New species and genera of the family Pickworthiidae" for Zoosystema, 2003, which is available online.

Harry Lee believes this is Sansonia iredalei (Bavay, 1922). I was cautious about this because Okutani's description calls the shell "light yellowish brown" and doesn't mention a brown protoconch. The illustration is equivocal about coloration but certainly the sculpture is very close.