How to open this without scratching the case? Vintage 40s bumper Omega

Recently picked this up and it's all original in great condition. It is a bumper and measures 32.5mm. However I can't get the back off. Whoever put the cashback on did so backwards so the notch for a tool is behind the crown and leaves no space for a tool to slide into to open it. I fear I may scratch the case as I have already left a small nick behind the crown trying to open it! Any thoughts?

The problem is that I can't find a good spot to wedge a tool into to pop the back off because the caseback is installed improperly... I'll have to give it to my watchmaker

Start with a razor blade to get a small gap before using a caseback opener.

I got a $30 Swiss Army knife and blunted the blade down so I don’t cut myself. This I use for casebacks like this and removing strap spring bars. Works very well. It has a thinner edge than a caseback tool.

If you can access one, scalpel is an even better option. As sharp as a razor blade, but more heft.

Gap for back is currently to the left of the crown. Bezel is to the right

Beautiful dial 😀

I have a collection of old master and visa cards which I have sharpened one end and use that end to wedge between case back and case.

I then get the case and hold it in a thick cloth, enough to get a good grip and to protect my hands from the sharp part of the card in a firm position.

I then get a small jewelers hammer and give it a firm tap on the flat edge of the card to get enough inertia between case back and case.

I find this works 9 out of 10 times as the card may not always work due to getting blunt. You can try to sharpen card edge if you are short of cards. I have never scratched a case using this method.

One of the very reasons I keep away from snap on case backs as you always run risk of scratches no matter how careful you are with ordinary case opening blades. I call them air cooled cases. If you have old credit cards lying around the house and you are confident, give it a try!!!