A member today posted this photo showing a complete instrument panel from a Soyuz TM capsule, and a globus instrument from a Voskhod capsule:
Both items are in their private collection. Only 5 Voskhod vessels ever flew, in 1964 and 1965. 34 Soyuz TM capsules were launched between 1986 and 2002.
So, the Voskhod spacecraft, in particular, were of great historical significance. And, like all crew capsules, these things were property of their governments, in this case the Soviet government. (Perhaps the Russian government in the case of the Soyuz panel, although it certainly doesn't look recent.) When I see such an item in a private collection, I must admit my reaction is '...What?...'.
How do such items end up on the market and get acquired? Is that still happening?
For context, the Voskhod flew during the Gemini Program. The capsules for Gemini flights are all in museums, and the Wikipedia entry for the program even has a section listing where each one is.