Consolidation of Darlot barrel and lens marking changes to help with dating?

[Lethargus]

I know Darlots are extremely hard to date, but I'm wondering if anyone has put together (or if we could do it as a community) known dates associated with their marking changes.

I'm aware of the old name pre 1860, followed by both names on 1860-1861 lenses, with 1861+ being the usual "Darlot Paris" seen most often.

Do we know when the crossed AD was added? Or if at any point it stopped being used? Because there are plenty of lenses without the crossed letters. Further, do we know when they stopped putting ink marks on the glass, or if there's any rhyme or reason to the marks on the older glass?

My interest in doing this has been reinvigorated by a recent acquisition. This lens is about 4" long with a cam but no waterhouse stops, so assumed it would be a projection lens triplet or something simple. It's marked "Darlot Paris - Made in France" with no other barrel markings, including no crossed AD. The lens is in great shape, so I assumed early 1900s. However, when I take it apart it's an honest Petzval and has quite a bit of writing that could be "4 N3 515 13 Darlot Paris" on the front lens pair and the larger rear lens matches with "4 515 Darlot Paris." This basically has many conflicting indicators based on what I've managed to collect, but it doesn't look like it's an amalgamation nor repair job.

So can we put rough dates to when Darlot changed their marking practices? I'm especially interested in when the crossed AD was either added or removed because I honestly haven't ruled out this being a very old counterfeit.

[Steven Tribe]

I know Darlots are extremely hard to date, but I'm wondering if anyone has put together (or if we could do it as a community) known dates associated with their marking changes.

I'm aware of the old name pre 1860, followed by both names on 1860-1861 lenses, with 1861+ being the usual "Darlot Paris" seen most often............

I have been involved in a number of these exercises. I don't think it is very easy and probably impossible with Darlot.
For instance, the various combinations of Jamin/Darlot have often (as you mention) been related to distinct periods after 1859. Personally, I think that it is more related to the connection each had with the product. A lens type that Jamin initiated would retain his name after Darlot took after the firm. Another product which was developed jointly by Jamin and Darlot had another agreed combination. Of course, part or all of the agreement may have been dissolved at his (Jamin's) death.

Another problem is the fact that low and high serial numbers were used at the same time for different products. Many of these serial numbers (for the Universal lens) are the same.

[Drew Bedo]

Isn't there a reference book on These lenses out there?

I found this one on Amazon: https://www.amazon.com/Photographic-.../dp/8883414918

Havent reqad it, so don't know if it would help.

[Steven Tribe]

THis is the D'Agostini book from 2011. Interesting in many ways, but not comprehensive.
There is also the le Reve edition booklet (no. 14) on Jamin/Darlot - which I havn't seen and it is out of print. These booklets were supposed to printed in 100 copies each!

I have also considering that the numbering chaos may have something to do with the various combination/variations of the Jamin/Darlot engraving. Perhaps Jamin had a "inventors fee" for every lens sold after his sale of th company to Darlot - use of 2 or 3 numbers series would a good way to keep a check of what was due to the retired Jamin.

[Lethargus]

I'm aware of the duplicate serial numbers, which is why I was hoping to focus on barrel markings and simply presence or absence of glass markings. I hadn't heard of both names appearing on anything outside the 60-61 range. That's why I was just hoping to get a consolidation of knowledge for general ranges. Such as lens markings not appearing after somewhere in the 1880's range. Maybe it's not doable but I was hoping enough others would have pieces of knowledge we could maybe put something together.

[Drew Bedo]

There may be another complicating dynamic at work.

IN looking at brass lenses on e-Bay, I am seeing incomplete lenses and parts offered. It is my suspicion that there is a bit of mix-and-match going on. I can imagine some unscrupulous seller finding an incomplete barrel with de4sirble/rare engraving marks swapping around enough parts to make a "complete" lens assembly and calling it an "estate find".