A real diamond, or synthetic, on an old wedding ring?

My grandmother ped away in 2002 and I recieved a ring, which is a wedding ring. I'm not sure if it was my grandmother's or her mother's, but I am thinking about using it as my wedding ring for my own wedding in October of this year. I am trying to find out if it is real. It is 10k white gold and has a very small marking in an oval on the inside of the band. I have tried to scratch gl with it and it did scratch the gl, but I can't tell if it scratched the gem because it is so shiny, I can't really see the outside of it, just all the glimmer. I know cubic zirconia didn't begin to get made until like 2001, and this is a very old ring. It has a large "diamond" in the middle and two smaller diamonds on the sides. If I look close at the large "diamond", I can see a greyish tint. It isn't gawdy, but it isn't extremely small. I am trying to measure it and it appears to be 5 or 6 mm across (it's round). I know my grandparents were married probably in the forties, possibly 1950, which I think (not sure, but I think) was before synthetic diamonds were made (?) Another thing: on the inside of the band, under where the diamonds are, there are small holes, directly under all the diamonds. What does that mean? Is that just how they used to set them, and does anyone know what time period that is from? I really love this ring and I will probably still use it as my wedding ring regardless, it would just be so cool if it were a real diamond. I keep trying to take a picture, but it's just too shiny and looks like a white blur. Any suggestions?