Stamps Courier From UK To Usa?

Hi Everybody!
Does anyone know a reliable courier service for (potentially) valuable stamps between UK and USA, please? ... ideally with a reliable insurance, as well :)
Thank you very much!
Augustin

I've had a few deliveries from the UK where the seller has used Pitney Bowes.

No problems at all and much quicker delivery than Royal Mail.

that's something I had to learn also. If you just found some stamps in an album of which you think they could be worth getting certified, there is no way to do a shipping with insurance.

If the letter is lost, any insurance in the world would like to see:
- either: your invoice if you bought the stamps
- or: any proof that the stamp was genuine (certified)

In the case of found stamps you don't have any of the two things. So if you want to send for certification it's at your own risk. That's what also German auction houses and FedEx told me. I didn't send anything across the ocean because of that until now, but I will do probably.

By the way: I don't understand why the shipping address of the PF is explicitly to "The Philatelic Foundation". If I would like to steal any letter, I would certainly look for addresses where I can guess that there is valuable content. It would be very good if the address for sending stamps would be something more neutral. How do you all resolve this problem? Do you only write "PF" on the letter? Or is there an alternative address?