I originally paid £104 for my inverse display M5610 back in July. Hoewever, I couldn't get over the illegibility of the screen and sold it on to a friend for £70.
Then, this morning I was browsing in a second hand electronics store and found the other version (perhaps older) for just £25. It is in mint condition, even the strap. I don't think the chap had any idea about Casios because he was also selling an older, non radio and non solar Casio for £35 - probably what it is worth new. This is a huge bargain for me as I was considering buying a new M5610, I missed its features, and this one just needs a little cleaning of dust from the screen.
I'm so happy to have this watch again as I like it and will use the time to correct my Raymond Weil Maestro which runs about half a minute slow a week.