Had an interesting time getting at the movement, but was well worth it, since it has clarified which movement is used and leads to a slight Movement Table amendment….

First though, here’s a look at the case and how to remove the back. The bracelet has to be removed first of all, which reveals a spring between each set of lugs:

The springs are pressed in to release the back:

The crown / stem is in two parts , which is loose once the back is removed since it’s secured by the upper case. Here’s the inside of the case back clearly showing the integral springs:

Looks like the case design was patented by Citizen from the mark inside the case back – this pic shows the loose crown / outer stem:

And here’s the movement, the number is stamped to the lower right of the balance wheel:

And the movement number? Turns out it’s 5204, which was introduced in 1965 in the Crystal Seven line, and was then found in the quirkily named ‘Dandy Seven Custom’ in 1968.

Putting it back together is of course the reverse of dismantling, with care needed both to keep the gasket inside the upper case correctly in place and to locate the lug on the outer stem in the inner part before pressing the back into place.