As you may guess, (?) represents an uncertainty - for example, when a crew member is believed to be a particular person, but the editor is not 100% that it is that person (e.g., Alan Berry(?)).
Any help with 'identifying' people in photos would be greatly appreciated, so if you see any question marks in brackets and what have you, feel free to edit the page and name the person / people! This message is particularly for any people who worked for Century 21 that may stumble across this page (you never know who's reading folks).
Oh, and enjoy what will soon be one of if not the biggest collections of behind-the-scenes photos relating to Captain Scarlet and the Mysterons!