Wick - first off beautiful job!
You might have the original silver tested - old German Silver with the often higher nickel content of 25-30% does not tarnish like the common modern 17% stuff does but more like coin silver.
If GS then post 1820's-30's, if real silver (coin or Sterling) than my SWAG would be last quarter of the 18th Century to mid 1800's.
Without a maker's mark also IMO US made, possibly in the south east. IIRC both Grant's and Minnis' books have a couple of similar daggers.