I have a footed sugar bowl and matching creamer, created in a yellowish hue. I can not recognize who the maker is.

Inisde each item, not stamped, but raised is the mark:

A diamond, with the letters RDD (the D's are much smaller than the R) inside and what looks like a crown created out of the top of the diamond. At the bottom of the diamond is the letter K at the top is the #4.

There is also another mark, outside of the diamond, which I can't work out what it is.

Diamond shaped pottery marks, printed or impressed on the base, are official marks of the Patent Office Registry of Designs, set up in 1842 to protect manufacturers from plagiarism and piracy.

There are so many marks I would start with this link below.. You should find your answer..

POTTERY MARKS | FAMOUS POTTERS - Home

Thanks for your help.

The number that relates to class is not IV but either II or III I can't seem to find what that denotes. ANy thoughts?