With thanks to a comment by ‘Art Van Deco’, I’ve added a second case number for the 67-9020 gold plated Challenge Timer (‘bullhead’). With his help I have been able to confirm that this model came with two case numbers – 4-901193 and 4-901029 – so I have added the second one to the article: https://sweep-hand.org/citizens-vintage-chronographs/

Thanks Art, it’s always good to add more information that other enthusiasts can provide 🙂