This looks a very nice little knife, by what the pics say.

I'd say late Victorian, but the silver work is high quality.
I see a rampant lion on the scabbard. Is it holding a letter or anything?
(as in a letter of the alphabet!)
If it Is holding a letter, it may give a clue to who it once belonged, seeing as it is not in a 'belt' so therefore giving the impression that it was the owners personal arms.
Much guessing in the above, as I'm not up on heraldry!