The extremely generalised wording of the message, the fact that the letter is not addressed to anyone at all, and the incomplete dating (to allow for a bulk mailing taking several days if necessary), are all classic indications of a facsimile.
John Wilson Manuscripts Limited, Painswick Lawn, 7 Painswick Road, CHELTENHAM GL50 2EZ, UK
Tel: +44(0)1242 580344 Fax: +44(0)1242 580355