philipk5

Try using a claw crystal lift tool first. If you are lucky it may not have been glued in. Good luck.

Whereabouts in the world are you ? Maybe there is someone nearby with a quartz movement tester / demagnetiser who would be willing and able to offer some advice once the problem is a little better identified? I am near Maidstone in Kent UK and would be willing to help.

If the internal diameter of the case measures 27.80mm then a 28.00 low dome acrylic should be able to be fitted using a "claw". It needs to be tight enough to provide some sort of seal and not fall out but not so tight it won't fit!!. If you use any sort of adhesive it will make removing the acrylic somewhat difficult in the future (probably next week when a proper case back turns up). Also make sure that the crystal doesn't foul the stem &/or pushers and any moving parts. Photos of your watch front & rear may remind someone they have something in their scrap bin? Hope this makes sense, and helps keep another watch in use. Cheers Phil.

Bonus points to clockboy and eezyrider ! Managed to open it. Apparently there are three lugs on the case back that are equally spaced and locate with corresponding notches on the case. Very easy to go past the opening point and as such re-lock it (Japanese sense of humour??). Here are some photos to clarify, also for future reference should anyone encounter one. Assuming this isn't the only one still in existence. Many thanks to all. Now just need to track down a replacement movement...….

Thanks for all the comments. It's not a conventional screw back - there are only four notches and an inscription for open and close. There is a very small amount of (very free) movement of about 5/10 degrees. I assume that a small turn and the back would drop off, but it doesn't and I am reluctant to "persuade" it until I have a better idea of exactly how it should come apart and hence then working out why it doesn't.

Any advice on opening this case back would be appreciated. Thanks in advance!

As a temporary measure you could fit a low dome acrylic?

I have been browsing this forum for a good few months now and have learnt a lot, for which I am grateful. I would describe myself as a keen amateur, usually working on the assertion that "If you think you can or you think you can't, you're probably right"! As a consequence I have an ever growing repairs pending box (mechanical growing, quartz reducing), and a relatively small scrap pile. I live near Maidstone in Kent south east England. Looking forward to playing a more active part here. Phil.