"My word is my bond," is the motto of what financial institution?

London Stock Exchange, among others.

"The Chartered Institute for Securities & Investment (CISI) has officially adopted the motto “My Word is My Bond” which will feature in its newly commissioned coat of arms. The motto, which is the English translation of the London Stock Exchange’s Latin motto ‘Dictum Meum Pactum’ confirms the CISI’s position as promoter of the highest standards of integrity and ethics within the securities and investment industry."

rfpconnect.com/news/2010/3/19/cisi-moves-forward-under-new-motto-my-word-is-my-bond no longer exists
https://www.cisi.org/cisiweb2/cisi-website/about-us/press-release/2017/02/10/cisi-celebrates-25th-anniversary-and-looks-ahead-to-supporting-the-next-generation-of-global-finance-professionals
https://jerichochambers.com/events/my-word-was-my-bond-ethics-and-the-city/