The meaning of the elements on a coat of arms differs from one to another and with the country and time when the coat of arms was created. The Star in the Australian Coat of Arms represents all of Australia's states.
A seal and coat of arms are not the same thing. A coat of arms is a unique heraldic symbol on a shield, tabard or surcoat. Unlike a seal, a coat of arms has a form description which is known as a blazon.
The blacksmith represented on the coat of arms is an knight's helmet over the flag of whatever country they work in and the country's colors in the coat of arms. See the related link for an example of the British blacksmith coat of arms.