You never know what you're going to find in those cryptically marked boxes. I recently came across a treasure trove of sketch books left to the Legation by Marguerite McBey, Tangier American artist, 1905 – 1999. Though her husband James was a better known artist (his portrait of Lawrence of Arabia hangs in the Imperial War Museum in London), both McBeys are synonymous with Tangier, where they lived for decades. The Legation museum is a repository for many of their works.
Google "John Carter Vincent" and you're likely to come up with few images, and none linking him with Tangier, which happened to be his last diplomatic assignment. Here's the anodyne reference to his Tangier stint from the State Department Office of the Historian:
Diplomatic Agent/Consul General (Morocco)
Appointed: June 9, 1951
Presentation of Credentials: June 26, 1951
Termination of Mission: Relinquished charge April 16, 1953
John Carter Vincent's time in Tangier was that of a semi-exile – he was set to be named US Ambassador to Costa Rica, but was ensnared in the McCarthy era recriminations over "who lost China?" Vincent appears to have been a victim, like other China Hands in the US Foreign Service, of honest reporting during his service in war-torn China.
We don't have much in the way of references to his short time in Tangier: Vincent was likely a witness to the pro-independence riots in Tangier in spring 1952. Foreign Relations of the United States (FRUS) details some of his reports as the US representative on the Tangier Committee of Control, the consortium of foreign "powers" that ran the International Zone.
Marguerite McBey's sketch of John Carter Vincent is dated 25/26 February, 1967 – years after Vincent was forced to resign from the State Department for the "faulty judgment" of predicting the Communist takeover of China (China Scapegoat: The Diplomatic Ordeal of John Carter Vincent by Gary May).
Pensive in McBey's sketch, perhaps reflecting on his ordeal with loyalty boards and Senate subcommittees, John Carter Vincent died five years later in 1972.