Need help with Antique silver mark

[ppri9146]

I have an unusual antique silver sifter spoon.  I am not sure if it is silverplate or Sterling.   It has an unusual maker's mark inside a diamond.  The pattern is also very unusual.  Any help in identifying the maker, the composition and the pattern would be greatly appreciated.  

[md1919]

that is the british design registration mark.  it is similar to a patent number, it tells when the design was registered.  it is not silver as it bears no british silver standard marks. this mark was used until 1883

[ppri9146]

Thanks so much. Do you think it is silverplate?