Often what happens is that after a razor has been screwed it sits in a drawer for sometimes generations before finally giving birth to a lovely new blade at the hands of our resident midwives (aka restorers).
Sexing razors is a tricky thing actually. Bit like chickens. Even if you do sex them correctly and try to breed them, they are worse than Pandas. I've even tried showing mine razor pron to no avail...
James.