Hi i notice a lot of people on here asking for info on lever locks well take yourself down to your local locksmith or shoe repairer (yes thats correct) and see if they can order you a book called " An Encyclopaedia of locks and builders hardware" by josiah parkes-union works-willenhall-england.
It has a brown hardback cover and is about 9inches by 6inches size
This book was first published in 1958 then 2nd print 1968 and 3rd print 1979. All this information is all i could find inside about print.
It is quite an old book and may be hard to get but i ordered mine when i was a shoe repairer about 5 years ago through one of my key suppliers at about Â£20 quid. It is a goldmine of info on most locks and will certainly educate you on most lever locks and general lock history.
Bearing in mind when this was written its amazing a lot of the locks havent changed that much just been modifiyed over time.
If this book doesnt open your eyes to how advanced locks can be take up knitting !!
It shows mushroom pins,side bar cylinders,deadlock levers,wards and much more.
Seek this book out
I am going to see a shoe repairer i used to with and see if it still available otherwise im sure a little "google" will help.