Identification of a brass Magic lantern lens

[Keith C]

Ive included a picture of the lens ( i think ) to aid in identification. From looking through previous magic lantern lens posts, here is what i feel like may be important info:
It has two lens elements. Not three
The only marking on it is "Arriere" (i cant figure out how to add the accent marks). This simply says "rear" in french. Because of that i would assume that this is not a pretzval lens.
measuring the outer brass barrel in the front this lens is about 60mm dia, and the glass at the front is 48mm in dia.
The actual lantern that it came from also has no markings. of course there is no guarantee that the lens and the lantern were originally sold together.

Thats all that i can think of to help.
Regardless of the lenses make, I will still try to use it to see how a photo turns out. To that end, one more nubee question; is there any online documentation on how to mount the lens to a lens board? If the threading on the lens is standard, then, awesome! If not, ack!!

Many thanks

[Steven Tribe]

It is a well made Petzval lens from around 1900. They have written "rear" on the rear lens because the front and rear threads are identical and the two cells can (and often are!) mounted incorrectly.
Threads were machine cut by this date (Metric) but there are no standardised diameters as the case is with shutters.
Quite often the anon. maker's name in written in pencil on the broader lens edges.
There is a universal iris type clamp for mounting lenses without flanges.

[Keith C]

So i looked around a lot more at Petzval lenses in general. am I right in thinking that Petzval is not a brand, but a "style", or some sort of unifying design element? when i first started looking around I had assumed that it was a brand.

[Steven Tribe]

Prof. Petzval designed a new optical layout which was much faster than the objectives in use in 1839/39. He collaborated with a number of opticians in Vienna (including Voigtlander and Waibl) in making and marketing the very successful design.
All his work with others seemed to end in strife!
The design was dominant for portrait photography and magic lanterns because of speed/brightness. It was eventually replaced by Cooke's triplet design for projection lenses as it was cheaper to produce (6 glass surfaces instead of 8).

see here
https://www.antiquecameras.net/petzvallens.html