Well, I received the P et P booklet covering Lerebours et Secretan. It is at least as comprehensive as any of the other sections I have seen. This is just a short reference relating to things taken up in this thread, I'll come back later with more!


1. Believe it or not- but our French friends have not discovered the micro scratching of seriai numbers on lenses which existed for a long period in the 1850's.

2. The cup inserts we have described here are called "Diaphragme emboite". They date this system as being from before 1855 and the central washer system as post 1855. And Waterhouse stops after 1860.

3. Serial numbers and Dates.

1839 - 1845. no serial numbers
1845. - 1850. 2000 to 5000
1850 - 1855. 5000 to 8000
1855. - 1860. 8000 to 11000
1860 - 1865. 11000 to 12900

Lowest number reported by them is 2012 and highest is 12609!