How to translate French "colleur"/"khôlleur" position into english? French higher education system is quite singular: besides traditional universities (following Bologna Process scheme with Bachelor (3 years), Master (2 years) and PhD (3 years)), there are so-called grandes écoles – mostly in the business and engineering fields. To enter a grande école, one must traditionally attend classes préparatoires.

One distinctive feature of these classes prépa is the significance of frequent colles (1 every two weeks per student and discipline – sometimes also written khôlles), which generally consist of  1 hour oral examination, where a couple of undergrads solve a problem in front of an examiner – the so-colled colleur.

Colleurs are mostly professors teaching in classe prépa. However they can also be university assistant professors, high-school teachers, PhD-candidates, or post-doc lecturing on their part time.

Question: What is the most appropriate translation of "colleur" into English?

("TA" or "tutor" both seem too broad in my opinion.)
I would suggest using the official title and then adding a brief sentence describing the job duties. This way you provide ask the information in an accurate and accessible way. Having to look up a job title is not a big deal when evaluating foreigners.