When giving anatomical positions or locations, o'clock is used instead of :00. This is typically the only time o'clock is used. This is one of those gray areas or exceptions to the rule. Likely the dictator said "twelve-thirty" position, so it would be best noted as "12:30 position." It would sound odd as 12:30 o'clock. What is the reason for using o'clock instead of :00 when giving anatomical positions or locations?
1) To follow a convention in anatomical terminology
2) To make it sound more precise
3) To avoid confusion with other time references
4) To emphasize the specific position or location