European IRRIDIZED Sponge-Ware Bowl- Bohemian?

When I saw this bowl in a flea market yesterday, I was sure that it was enamelware but after looking at it closely, I realized that it was actually Pottery with an outer Irridized (luster) glaze of black & red spongeware finish and an inner Irridized blue & white spongeware finish. It has a raised base with the letters 870/3 and has a gold-trimmed rim. It measures 7 1/2" in diameter and 3 1/8" tall. It also reminds me of the Wedgwood Fairyland Luster bowls without the fairies & birds. With that number mark under-base and no other marks, is this bowl continental European or N. American and by whom? Thanks everyone, RER(BOB)