The following item is currently listed for sale on ebay, the bidding to start at £15. The vendor seems aware that it ought to be in an archives office.
Old doctors ledger, patient notes and accounts.
Dr. Walshman, Kennington area of London 1799 - 1824.
Includes some of his letters, sent by Two Penny Post (pre penny black postage days), these are collectable and sought after, in their own right.