The website AtomHistory.ru published a very interesting document from the early days of the Soviet nuclear weapons program. It's the first page of the Decision of the Council of Ministers regarding the program of nuclear tests in 1953. (Thank you to the Centre for Analysis of Strategies and Technologies for posting the document on their blog). Among other aspects, the document provides some details about the amounts of fissile materials used in the first Soviet nuclear weapons.
It is clearly marked as "Declassified" on top of its original "Top Secret/Special Folder" classification. As it was the case with most documents at that level of secrecy, some words were written in by hand – the information was too sensitive to entrust it to typists. The hand-written words are in italics. These precautions notwithstanding, the document does not refer to fissile materials by their actual names – plutonium is "tellurium-120" and uranium is "tin-115" (this is a bit strange – in earlier documents plutonium was "ametil" and uranium – "kremnil"). "Test site No. 2" is the Semipalatinsk Test Site. […]
See this original blog post on russianforces.org