Need help with changing the battery on a Baume & Mercier 65811 Promesse

[MayerK]

I'm pretty new to watch repair and a friend gave me their Baume & Mercier 65811 Promesse watch to change the battery. I was able to remove the case back easily enough, just 4 screws, but got stumped after that. The battery is covered by a covering that extends beyond where the battery is and there are 3 screws to remove it. Having not encountered this before, I am hesitant to simply remove the screws in fear that I might dislodge something else. Does anyone have experience with this and is it safe to remove the covering?

I've attached an image of what it looks like.

Thanks in advance!

[AndyGSi]

I'd look at just removing the top right screw first on the battery cap and see if it will slide out.

Have you removed the stem and will the movement come out of the case?

Edit

What is the actual number of the movement?

Edited January 9 by AndyGSi

[Mercurial]

The movement looks like an ISA 257, but the battery cover plate is different to the examples of this movement that I have seen. 

I think AndyGSi’s suggestion of removing just the top right screw should work.
 

 

[AndyGSi]

2 minutes ago, Mercurial said:

The movement looks like an ISA 257, but the battery cover plate is different to the examples of this movement that I have seen. 

There's something before the .257 that I can't quite make out.

[Mercurial]

Well spotted!

I did my best (within what I can do from my phone) to enhance the markings and it looks to me like it says :

ISA SWISS 257

SWISS MADE

2 TWO JEWELS

E5

 

edit : fixed typo 

Edited January 9 by Mercurial

[AndyGSi]

1 hour ago, Mercurial said:

Well spotted!

I did my best (within what I can do from my phone) to enhance the markings and it looks to me like it says :

ISA SWISS 257

SWISS MADE

2 TWO JEWELS

E5

That's what I'd got too but can't find anything like it.

[Mercurial]

Other than the plate that covers the battery, these look very close, if not identical. 

 

I suspect the OP’s movement is an early ISA 257, made in Switzerland, and the ones seen online and that I’ve worked on are more recently made, sometimes of Switzerland. 

Mark

[MayerK]

Sorry to all of you for not responding sooner. My life got very hectic all of a sudden.

Thank you for the suggesting to loosening the one screw, that did the trick!

It got even more bizarre after that as the whole movement came out of the case and I had to reorient it back the way it was. It was nerve wracking but I managed it.

 

Thank you all for responding!