Saint Etienne 1892 - Calibre .22
Revolver 92 converted to 6mm.
As you will see, the barrel has been changed (and is much longer, with a derivable front sight), inserts reducing the caliber to 6 mm have been put in the chambers,
the firing pin well has been plugged and a rimfire system replaces
it, the hammer firing pin has been cut.
This is a known variant of the 92, but not very common.
Saint Etienne 1892 - Calibre .22
And here
is another 1892 in .22 caliber but this one doesn't have the long barrel!