Not exactly 'watchmaking' but need some advice

I'm just guessing here until someone who knows about these watches chimes in. That battery cover looks like it's for marking when the battery was replaced last, not necessarily to replace it. I would look around the caseback to see if you see a notch to stick a case knife in.

I believe this is a pre-quartz watch with an actual balance wheel. Did it tick when it was working?

Interesting looking watch. I have a fondness for dynamics, so it is interesting to see other takes on the design.

Could be a front loader. Which would be why there is no way to remove the back cover.

The 12 numbers on the battery cover seem odd. Combination lock, 9L, 3R, 2? If I had it I would try a rubber ball first. Not sure I would want to pry it though. The triangle looks like it is meant to be turned to that point.

Might be an electric watch which was a hybrid, where the battery rewound a small mainspring. I think there was a version what used a single transistor and contact switch to impulse the balance.

Hopefully we will have luck and someone else has seen one of these.

The engraving is unusual, "In memory of ..."

Looks like a snap back.

Check out this example on eBay, mainly the photos of the back.

https://www.ebay.com.au/itm/361694557873

Well there you go