Dorothy King  has unexpectedly  posted on her blog, photos of a number of items from the St Clair Archive at the British Museum. This archive includes amongst other things, the only surviving translation of the firman that it is claimed permitted Elgin to take the marbles  and the first letter from Greece requesting the return of marbles .
You can read her own introduction to the items from the archive (& her reasons for posting them online) here .
A full list of all her posts relating to the archive is available here .
Each post contains an overview, followed by additional posts that show more detailed photos, so that in most cases it should be possible to read the text. It is suggested that if you are interested in studying these items, you download them, in case at some later date they become unavailable.