Based in the eponymous city, Kharkov Velocipyed Zavod (Харьковский Велосипедный Завод which I believe translates as ‘Kharkov Bicycle Factory’) was a major volume manufacturer of bicycles in the USSR.
Alexander Leutner, a Baltic-German businessman established Alexander Leutner & Co. in 1886 in Riga (now in Latvia), to manufacture bicycles. It rapidly became one of the largest bicycle manufacturers in the Russian Empire. In 1915 Alexander Leutner and Co. were evacuated to Kharkov to avoid the advancing Imperial German Army. In 1923, after the revolution, the factory was taken into state ownership and became Kharkov Velocipyed Zavod. At some point the the factory was named after G.I Petrovsky, a prominent Ukrainian Bolshevik.
It is possible that Kharkov’s higher spec. models were some of the better bicycles manufactured in the USSR. At its peak Kharkov manufactured over 1,000,000 bicycles a year.
As discussed on the Brands page of this site, the components are stamped with three letters. These look like ‘XB3’ (so the brand is sometimes called this in the West) but these are actually Cyrillic letters that can be romanised as ‘KVZ’. Sometimes the company is also referred to as ‘HVZ’, and Arnfried Schmitz refers to it as ‘Charkow’. Kharkov is obviously a difficult word to romanise!
According to posts on bikelist.org the company seems to have been still in business in 2003, after possibly being bought by new owners in 2001. The US visitor who posted the comments seemed to be disturbed that there were still large posters of Lenin in the company’s offices (although I have my suspicions that the pictures may have featured G.I. Petrovsky - who, as a young man, was a passable a Lenin lookalike)! It appears that, by 2003, Kharkov had given up manufacturing their own aluminium derailleurs, but it is unclear whether they continue to make steel derailleurs.
Another site chronicles a visit to the Kharkov factory that may have been as recent as 2009. This site also shows a catalogue with bikes with relatively modern parts that use Kharkov derailleurs. Finally the Kharkov factory was proudly displaying a sample wheel from the astounding Lunokhod - and apparently claimed that it manufactured the wheels for the Lunokhods.
Over the years, Kharkov appear to have manufactured a considerable number of different derailleurs to use on their bicycles: