From the Herschel Shanks article:

Who Owns the Codex Sinaiticus?
The Monks at Mt. Sinai got Conned?

(Only in 1869, when a somewhat mysterious ratification of the gift was executed, was the manuscript removed from the Ministry of Foreign Affairs and placed in the Imperial Public Library of St. Petersburg.)

... It was left to Cyril’s successor, Archbishop Cal-listratus, to provide the Russian authorities with a confirmatory deed of gift. This was done only in 1869, 10 years after Tischendorf had taken the manuscript from the monastery. Although the deed of gift has often been referred to since then and even quoted in existing documents, it has yet to be published. Sevcenko says that his investigation indicates that the deed of gift was obtained “by the use of pressures that deserve closer scrutiny”6 Callistratus himself expressed “bitter complaints” that the manuscript had been “purloined” from the monastery.7 In the words of the Russian diplomat who negotiated the “donation,” he wanted to put “an end to the story of the Sinai Bible [that had been] stolen by us.”8
This 1869 ratification only came forward much later. It is thought to be a quid pro quo, given under pressure, for a Sinai gift, after Russian meddling in the monastery politics. And, let's remember, Simonides was working in the historical archives in St. Petersburg in 1869.

On this thread we will try to collate any information about this ratification.

e.g. Is it accepted as authentic without doubt by Sinai monastery? Do they have a copy?