Royal Winton Platter

I found this Royal Winton platter recently in Brisbane. I am strangely attracted to those charcoal splotches which I think was deliberate. My friend thinks the splotches make the platter look dirty. I don't think it was a result of ageing etc. From my research, the mark dates from the 1920s-1930. I had originally suspected this to be a 1930s piece when I saw it and its larger companion in a thrift shop. But the larger one was very well worn with the green edging faded and worn off.