So what happened here? Did the seller have surplus nomos straps that they refitted to sell? Did some "fall off a truck"? Or were they falsely stamped with the original intent to sell a fake Nomos strap?
Larger strap manufacturers will often make deals with many companies. It's entirely possible you've got a surplus Nomos strap that was rebuilt/sold as a general strap.
When it comes to shell cordovan or other premium leathers, any schmuck (like me) can buy it in to make+sell a strap online, and sell for a huge premium regardless of their skill. There are many Etsy sellers who sell trash quality basic straps at an overpriced point that does not reflect their skill level - but you wouldn't notice the details unless you're a leatherworker yourself.
The opposite is also true, you can get incredible handmade straps for a good price from more humble sellers - the best thing to look for I guess is reputable reviews and quantity sold, or at least traders that have sold the same stuff for a few years.
A note from a small time leatherworker - "Genuine leather" "Leather" and other similar titles mean NOTHING.
Leather can be glued together from scraps, much like wood, and then marketed as "100% leather", and "Genuine Leather" can be any quality, any piece, (therefore generally lowest quality + cheapest) and is generally used to pull the wool over consumers' eyes.
Full Grain usually means top quality, it means you're getting the best part* of the piece of leather - generally speaking. Full grain leather is ideal for a watch band. For a watch strap, you want a more breathable leather stiched to the inside of the band - most manufacturers use thin calf leather for its fine grain and it's thin profile.
(* this is true for a generic standard piece of leather - it means you're getting the top-natural-skin side piece, and is usually the most expensive part of a piece of leather - the flesh side can be sold cheaper. Suede etc is a different beast, and crocodile/ostrich/shell cordovan are more literally different beasts)
https://www.stowa.de/Flieger+Klassik+Baumuster+B.htm
Flieger style watches Type B have similar enough designs here. If you like the link above, Laco do cheaper watches in the same style. Other brands such as Seiko (snk007) are even cheaper. Fore more expensive options, there are watches in this style from IWC, and vintage models from Glashutte Original to name a few - but this is a deep topic.
Enjoy!
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