My guess is..... Umm... Somewhere between the three I have and eleventy billion.

Seriously though, I would say definitely hundreds of thousands and most likely millions. Bear in mind the company was around for the best part of the 19th century and was based in one of the biggest steel making cities in the world. W&B's were probably one of the most common blades around back then.

On a vaguely related note, I had a dream the other night that I had a time machine and went back through time picking up all these wonderful blades brand new off the production line. Then I woke up and realised I didnt have most of them!