Alloy bodied vehicles don't use a pure alloy a such, its a mixture alloy of aluminium and magnesium

Land Rover's (& I assume other makers) alloy bodies are made from Birmabright, Birmabright is merely a trade name of the old Birmetals Co. (located in Birmingham) for a British standard specification of sheet, ... (it is actually NS4 std).
All the major aluminium rolling mills - Alcan, Pechiney, British Aluminium, High Duty Alloys, Alcoa etc. sold the same sheet either under their trade-name or under the relevant British specification.

for more try this link (Wikipedia)


nb: I'm an Australian, we're a lazy mob when it comes to speech, therefore Alloy = Aluminum
(alloy is quicker to type and easier to spell, same shyte/different name)