Tchaikovsky Piano Sonata in C-sharp minor, Op. Posth. 80

[jaxpiano]

Composed in 1865, not published during Tchaikovsky's lifetime... anybody know anything about it?

Here's what I know:
Gilels recording (live) from the 1960s
Four editions (none of which is definitive ... edited by Tanyev?)
Original manuscript lost since 1901
Scherzo of Sonata same as (similar to) Symphony No. 1