Unless anyone can suggest a reason why I shouldn't, I will use this thread to build up a table of lens types from Wallet, Hermagis & Derogy and Derogy from around 1855 until about 1865. There are a number of different engravings, serial numbers/no serial numbers lens edge markings etc.
There is some data in D'Agostini and le reve edition, but I think we can do better!
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