What must rubber personnel protective insulating equipment be marked with?

Rubber personnel protective insulating equipment, such as gloves and blankets used in electrical work, must be marked with a voltage rating and an expiration date to ensure their safety and effectiveness. The voltage rating indicates the maximum voltage the equipment can safely withstand, which is critical for preventing electrical shock during use. The expiration date is equally important because rubber can degrade over time due to environmental factors, usage, and wear, which can compromise its insulating properties. This marking provides essential information to users, allowing them to assess whether the equipment is still suitable for safe operation in their specific working conditions.

While other options might include useful information about the equipment, they do not fulfill the critical safety requirements outlined for insulating gear. Thus, focusing on voltage rating and expiration date is crucial for ensuring that personnel are adequately protected in electrical environments.