So I am doing my undergrad research paper on the Boston Massacre, and I am using LH Butterfield & Hiller Zobel's book The Legal Papers of John Adams. They cited a source called "Anonymous summary of crown evidence". It is in PRO C.O. 5:759, p. 711-720. Originally an enclosure in Hutchinson to Hillsbourough, 20 Nov. 1770. So I have uncovered that PRO C.O. stands for the Public Records Office, Colonial Office. That is where I have hit a wall. After searching google for the source cited, I keep getting the Legal Papers, with no one actually finding the original source. Please help guys!
It's from the archives of the British Colonial Office, which wasn't created until 1854, but has records from its predecessor offices going back to the 16th century.
They are held in the British National Archives, but Princeton University seems to have microfilm copies.