Zum. 9 - Presumed Forgery, If So, Is It A Well Known Forger?

I recently picked up this letter with what would be a very rare stamp on it if it's real. I bought this for relatively little, presuming it was a forgery for a variety of reasons.
I know some people actually collect forgeries from some of the more famous forgers.
Just curious if people are familiar with this one?
My guess is someone took an old letter an affixed this stamp to it after the fact. Aside from the postmarks on the envelope appearing to be much later than would be expected (1856), and the extensions of the cancellation lines onto the envelope looking like they were added after the fact, is there something glaringly obvious about the stamp itself that stands out?
*Edit* I added a photo comparing it to an original for reference.
Thanks in advance for any feedback.

Looking at some originals on some auction sites, a lot of things are jumping out at me. The first was the black cross outline which these stamps didn't have. It's weird that a forger would make an obvious mistake like that but maybe they were also referencing the later Poste Locale stamps.
Lots of other give aways, like the font on the 4 and a bunch of the details, but a person would need to either be intimately familiar with the stamp design or have a reference with them if they stumbled on this in the wild and wanted to be confident about their purchase.
I find the whole forgery aspect of stamp collecting fascinating.
If anyone knows if a famous forger was behind this, would love to know.
Thanks
Kurt

Looks like the original stamp was removed (partial vertical cancel lines under the forged stamp).Perhaps the original stamp was defective? Yes, a clumsy job at that...

The glaring feature to me are the uneven background lines. If you are prowling out in the wild, then your phone is your reference. There are tiny differences in the 4c designs from stamp to stamp in the sheet of 100 but are essentially the same, unlike the 5c that had differences in the "5" when the printing stone for the 4c sheet was re-used.

Now I don't know Swiss covers of this period at all. But (La) Chaux-de-Fonds is/was in Neuchatel Canton (see also the corner card) that had its own stamp in 1850 and this design was issued by Vaud Canton. Interesting that a Neuchatel stamp could possibly have been on this cover originally(!!??). I've checked the Jäggli-Weber cancel book and can't find a match for the thin bars cancel on the cover (if genuine).

There are a lot of different forgeries of early Switzerland. It's too poor quality to be a Sperati. See the Frajola site: https://www.sperati.org/SPAindex.htm under "transitional" issues. The answer will probably be in Nationalmarken Schweiz, Echt - Falsch - Verfälscht by Richard Shäfer, with color photos.

Thank you for the feedback about this. I've checked that site and maybe someday will pick up the book you mentioned.
My guess is that what was originally on this letter was a Strubel, based on the date, but I don't expect to ever know for sure.
It's certainly interesting to see counterfeits in action.

One must ask themselves whether a stamp belongs on a folded letter or not! Since the date stamps on this letter are 1856 there is no way this stamp belongs. Also, the crayon marking that looks like a large "N" actually represents "40" which was the correct fee for an unfranked letter to France, so no stamps ever belonged on this letter. The recipient paid 40 centimes to receive the letter.

Specialist knowledge on display, is a beautiful thing.

@deCoppet - we're now in very unfamiliar territory to me.
I appreciate your feedback, but could you clarify further about stamps and folded letters?
Are you saying that was something that was not done, or not done until later years?
I just purchased a few letters in auctions that may be connected to my ancestors, and they included a couple folded letters with strubels on them. I belive they are from a few years later, around 1860. I bought them just for the apparent possible connection to my roots, but am curious if you can point me towards more infirmation about folded letters in that era and if they ever had stamps or not?
Thank you so much.
Kurt

Hello Ruckus - folded letters were typical for the period until the mid to late 1870s. Postage was based on weight and many didn't want to pay for an extra cover sheet or an envelope. As postal sytems introduced postal envelopes is was assumed that a normal letter would travel at the single weight rate. Switzerland introduced these envelopes in 1868, England, I think in 1841!
So to answer your questions - folded letters had both stamps and no stamps. Then one must learn what the rate was for a letter to travel, whether within Switzerland or to a foreign country. There are many markings that can be found on pre-UPU letters since just about every country had a different agreement with Switzerland and each other. It was an accountants nightmare keeping track of all the different rates the primary reason for the UPU to be established in 1875. Strubels are pretty straight forward with very few known forgeries are known used on letters. And they can be identified easily when on cover, and with not much difficulty off cover.

Great info, deCoppet. (By the way, I like your cancels.)