Hi Cathy, Jan Plichta was a wholesaler active between 1930 and 1950, so your cat is going to be from between these dates.
Because each item is hand painted there is always a lot of leeway for differences in the design. Often this is how a painter can be identified by someone who has made a study of the pottery, although I couldn't say anything other than the cabbage roses which were the trade mark of Karel Nekola - there is a lot of information in the links we have given you, so I hope you will enjoy reading about Plichta and Wemyss!