Sun ISO 03 sandwich bodies are designed for multi-functional use to permit maximum circuit flexibility. To provide this versatility, most ISO 03 sandwich bodies do not have counterbores for installing O-ring seals. Instead, these bodies use a special seal retainer plate with a raised "Nib" and a locating "Notch". A corresponding nib locating hole and notch locating arrows are included on applicable ISO 03 sandwich bodies to ensure proper plate alignment. For those ISO 03 sandwich bodies where rotation is not functionally feasible, counterbores are included on the sealing faces and no retainer plate is required.