A Torah scroll is a communal object. It is commissioned by a congregation, used by it for generations, and repaired rather than replaced. When a community ends, the scroll does not.
More than fifteen hundred scrolls from the Jewish communities of Bohemia and Moravia were gathered at the Michle synagogue in Prague during the Second World War, along with a vast quantity of other communal property, assembled by Jewish curators working under German authority as their communities were deported and murdered. What the assembly was intended for has been argued over since; what it produced was a warehouse of scrolls whose congregations no longer existed.
They passed to the postwar Czechoslovak state and in 1964 were bought and brought to Westminster Synagogue in London. From there they have been distributed on permanent loan to congregations worldwide, restored where restoration was possible. Many are used in services now. Some are beyond repair and are kept unrolled as they are, which is a decision about memory rather than about ritual fitness, since an unfit scroll cannot be read from.
A congregation holding one is generally aware of which town it came from. That is the point of the arrangement: the scroll is not a relic of a community but the continuation of its use, read from on a Saturday morning by people who are not its descendants and who know whose it was.