Another update today – first I’ve added a pic of an orange dialled 52-0110 kindly sent to me by Martin (Martback).
Second I found a pic of a rather battered 62-6198 box, which shows that it was known as a ‘Challenge Diver‘. It may be other models from the 1970s were also known as this, echoing the ‘Challenge Timer’ name give to Citizen’s range of chronographs during the same period.
Thirdly, although this is not an update to the page, I have been searching and searching for another blue dialled example of the 52-0110, but with no luck so far. If you spot anything please let me know!
Sweephand's Vintage Citizen Watch Blog 
Excellent find that “Challenge diver” name! I had to do some research on that. It seems that atleast 52-0110 also was using this name: http://tokeibakai.exblog.jp/17252830/
Mikko
Hi Mikko, great find – I’ll put that link in the Diver Page. It confirms what I thought, that a number of 1970s models were called Challenge Divers. Thanks for posting the link here,
Stephen
Found also found this emaizing story about durability of these divers:
“In June 1983, a clock that is covered with mussels found in Sydney, Australia by someone who was walking on the beach. “I can only guess that it was a watch because the entire surface is coated by a mussel watch”. He took the watch to go home and clean it. At that time, he realized that the clock still works! Stunned by his discovery, he contacted CITIZEN Australia.
After a thorough search, CITIZEN HQ ultimately ensure that the clock is “Diver Challenge”, which was launched in 1977.”
See the picture of the watch at: http://m.kaskus.co.id/post/52089e7fe474b4c521000002
Thanks for this Mikko – worthy of a post I think 🙂 Mind you that bezel insert will have to be replaced!
Stephen