I have this style caseback for two of my 1958 omega geneves and i can't figure out how to open them, there is no notches, no spaces to put a case opening or knife either.
Doesn't look very Omega-ish at first glance, but if you look very closely all around with a loupe, you will probably find a little notch somewhere. Remember, it can be anywhere.
But it's not gold-capped SS, is it. It's gold-plated base metal. You can see the brassing on the back of the lower right lug. Like Norm, I'd like to see the rest of the watch.