The guys raise some interesting points, but I believe this is all original.
The blade condition does not look great from the maker mark pic you have provided - it shows some staining and wear. I'd like to see the other side of the blade as well if possible. But, from these pics, it looks like the condition is commensurate with the rest of the knife. This may not have been removed from the scabbard often, which, when this happens, often leaves a blade that does not appear to 'match' the rest of the knife, or dagger.
It looks to have been stored poorly, leaving rusty looking plate loss to the steel hilt. The plates look well fitted, but a reverse pic would be good also.
It appears to have a nice motto, from what I can see in the pic provided, but not having the diamond would make it less desireable to most collectors.
I don't think this would be a parts piece because, if the blade is in a very good condition, with a nice motto, it makes no sense to pair it with a very rough hilt with no diamond.
Regards
Russ