Edwin M. Knowles China Co. Square Plate

Hello,
I purchased 5 of these small square plates at a thrift store in NC. All of the plates are the same size, shape, colors with the same "vase" logo stamped on the back. Three plates are stamped "30-2-4" and two are stamped "30-2-5".

Although I've searched several sites online and found information on the Edwin M. Knowles China Co, I have not found a picture nor information on these exact plates. I have learned that the logo printed on the back of each plate is an earlier print and that the first number correspondes to the year made; 1930.

Does anyone know any information on these specific plates or a price which these could sell in today's market?

Thanks!

Josh