Final answer:
The initial diameter of the steel specimen is already provided in the question as 0.503 inches.
Step-by-step explanation:
The initial diameter of the steel specimen is provided in the first sentence and is 0.503 inches. The information given about the gauge length and the state of the steel (elastic and plastic) is relevant to the question. However, the answer to the asked question is explicitly mentioned at the beginning. Therefore, the initial diameter of the steel specimen is 0.503 inches (option 1).