are you sure they're left hand threads? as far as I know, no BB ever made has a left hand threaded adjustable (non-drive) side cup, they're all right hand threaded. It's only the fixed (drive side) cup that can be either left or right hand threading, depending on standard:
british standard is left hand threaded
italian is right hand
french is right hand
swiss is the same pitch (35x1) as french, but left hand
so if you have a 35x1 BB with both cups the same "hand", then it's likely that you're confusing left and right hand threading, and the BB is swiss (which are rare)
If it's 35x1 and each side threads a different direction, then it's french (which are rare, but not as rare as swiss).