en.wikipedia.org/wiki/Pavel_Tretyakov

The Tretyakov Gallery’s own history page contradicts this wording directly. It says that although 1856 is considered the Gallery’s founding year, earlier in 1854–1855 Tretyakov bought 11 graphic sheets and 9 paintings by old Dutch masters. That means the article’s claim that his first purchase was “10 canvases” is not accurate: both the quantity and the description of what he bought differ from the museum’s account.

A separate Tretyakov Gallery Magazine article also describes 1856 as the year Tretyakov bought his first two paintings by Russian artists, which further shows that the museum distinguishes those later Russian purchases from the earlier Dutch acquisitions.

The article’s parenthetical dates for Sergei Tretyakov are off by a decade. The Tretyakov Gallery’s family-history page lists Pavel’s siblings and gives Sergei’s dates as 1834–1892. A Tretyakov Gallery Magazine article likewise identifies him as Sergei Mikhailovich Tretyakov (1834–1892).

So while the article is correct that Sergei died in 1892, the 1824 birth year is contradicted by the museum’s own historical material.