Voltaire is writing to the sister of M. Du Châtelet about financial matters relating to Cirey, following the death of her sister-in-law. It is understandable why Voltaire would have wanted to keep a copy of such an important document for his own records.
The manuscript bears in the top left corner of the first page an upper case ‘E’, probably signifying ‘envoyé’ which one finds on many file copies of letters send by Voltaire. He himself has added the addressee’s name and the date at the top of the first leaf, which shows much uncertainty regarding the month: originally ‘decembre’ became ‘septembre’, which was finally corrected to ‘nbre’ below the line.
A later librarian or editor has written the number ‘no. 127’ below the ‘E’ in the upper left corner.