Just use comparable items from approx same time period !! That can be established by the mark !! For dinnerware exact dates are rarely possible because they may have made that pattern for several years,, and if it sold well may have repeated it,, so just a general guideline is fine !!
There are no individual artists on this type dinnerware ,, all was produced same as today,, with machines and transfers !! Your little floral is transfer ware,, same as using a decal !!