Lockhart and Co
The short-lived partnership was established in 1787 at 36 Pall Mall as Lockhart, James and James. In 1793 The firm became Lockharts and Maxtone; in the following year Lockharts, Maxtone and Clark; and in 1797 appears for the last time as Lockharts, Maxtone, Wallis and Paterson. It was absorbed by Ransom and Co in 1798.
Material available at Group Archives: examples of cheques