As far as I can remember and I took every nut and bolt off my S Type during its rebuild I never saw a seal like that on my UK market built car.

 

So perhaps only for export to the USA where and are rules more severe

 

SA built cars with genuine Britax belts did not have that seal. I see it has Jaguar on it. Maybe it is a homologation thing for export like the LHS wheelarch plate on British cars.

 

I informed about the seals at Jag-lovers.com and got two answers which I will copy here.
In short it was believed to to certify that the seatbelts were of the correct US spec.

Hi, Yes my 65 OTS E type had the same lead sealed strap around the eye hook for the seatbelt. I cut the wire strapping, zinc plated it and re soldered it back on the eye hook. Believe it was to certify that the seatbelts were of the correct US spec.
Regards,
Allen

I was stripping the floorboards of my '65 Mk10 the other day and found the identical tags on all 4, although I haven’t looked closely at the imprint. It’s nice to know that it’s a factory part.
Ron

 

Makes sense!