In September 2018 Ebay seller sunart (aka bulart2004) from Bulgaria was trying to sell these reproduction early (1930s) Bulgarian enamelled plates. They are for sale at ridiculously high prices and actually there are other Bulgarian sellers who have genuine used ones for much less money.
The main problem with them is that they do not have the official seal/makers mark on them and they are obviously reproductions even though the seller says they are genuine, used.
Although I am no expert on these old Bulgarian plates, I have checked with a very knowledgeable plate man in Bulgaria who confirms „These plates are reproduction, missing stamp and the quality is new“.
Why spend hundreds of dollars on reproductions when you can fairly easily buy the real thing for less?