I was able to register my Tamron AF 150-500 mm F/5-6.7 Di III VC VXD, Sony E (item no. 06A-057.S), which I bought at Digitec.ch at https://www.mytamron.ch for the 10-year warranty.

I decided on the Tamron AF 50-400mm F/4.5-6.3 Di III VC VXD and bought the lens at digitec.ch. There was a sticker on the packaging with a code for the 10-year Swiss warranty. There was also an information sheet for the warranty in the packaging. I had to register the lens on https://www.mytamron.ch and so the 10-year Swiss warranty is valid.

I only found out whether the 10-year warranty was possible when I received the lens. On the product page of digitec.ch and also when ordering, there was no indication that the warranty could be extended. Digitec.ch should provide better information here.

The problem will be, as Rogerhu123 has written, that digitec.ch buys the lenses through several channels and not exclusively through the Swiss importer. Whether I have a warranty of 2 or 10 years makes a big difference and is certainly also a deciding factor when buying.

A statement from digitec.ch would be interesting!

I was able to extend it. Digitec usually states if it is imported goods, so you usually have the choice as a buyer of something cheaper for a few trade-offs.

Bought the Tamron AF 150-500 mm F/5-6.7 Di III VC VXD, Sony E at Digitec. Sent for warranty extension 10 years, where Tamron is advertised my purchase contract and series number of the lens. The answer from mytamron was that they could not find a serial number. Although mytamron also lists Digitec as the dealer. That is why my warranty extension was rejected. Strange. The next lens will be from a different manufacturer.

Thanks for the answers
Timokilche could extend the warranty but Rogerhu123 could not !

Addition to my answer. Even at Digitec.ch, I have a guarantee period until 2031 in the customer area.

No. I could not extend my lens.