From the pics, it looks like a Yataghan bayonet, possibly for a Snider short rifle, with what appear to be Liege inspectors' view marks (any markings on the other side?). The specific rifle it was meant for would depend on the attachment arrangement on it, as they were used on a large variety of rifle types.
Value depends on the usual specifics...condition and scarcity of the variant.
Definitely appears to be a British yataghan-style sword bayonet, but precisely which model is always a joy to try to determine ... i.e. Pattern 1856, Pattern 1858, etc.
One clue however ... assuming the scabbard is original to the bayonet ... although I'm not at home to access my references, as I recall the "all steel" scabbard your bayonet appears to have (as opposed to the more commonly seen leather scabbard with steel tip and throat) was only used with the British Artillery Pattern yataghan bayonet ... can't recall the "pattern year" off the top of my head ... P'1860?