Hello,Welcome and thanks for your question. The answer is No.
Most artists will want to stamp not just the purity of the gold, but want their mark on it as well. Artist pieces made before 1900 rarely were stamped with karat.
what is the answer yes or no
Why have you given me a negative rating?
There is no yes or no answer.
There is no legal requirement that it be stamped, but most artists choose to stamp both the purity and their maker's mark on it..