I believe this is a cake knife. It is certainly not part of a place setting. It has a serated edge and a blade long enough to reach into the center of a good sized cake.
It is from Birks Silver and is part of the Regency Plate line. It began production in 1997 and is still being manufactured. This classic pattern is Tudor, which is identical to the Birks sterling pattern, Saxon, a very old pattern. If you are collecting Saxon and the budget is tight, you can intermix Tudor and no one will know unless they pick up the magnifying lens.
This knife is 10 inches and is in excellent condition. I have other pieces in the same pattern that are as new.