Hey Mario,
The pic on my phone makes the belly look unlike any that I have ever seen. Or maybe you can lay the graver on a black sheet of paper for a clearer view.
The two measurements shown are unnecessary, as it is the actual cutting face that matters and those dimensions will vary depending on what you're cutting.
One tool may be 1.0 mm wide while others progress up to around 3.0 mm wide or wider.
i occasionally make up specialty gravers, for work where the others just won't do. the nice thing about store-bought gravers-- you know from the start that they are the proper hardness. they come in all manner of configurations, and they come in graded sizes. you could do all this on your own, but think of the time you'll spend. time better spent on other areas. not only that, but quite a variety of steels are available-- carbide, momax, purple label, hss, glen steel-- just to name a few. if you have the money, far better to buy the commercially made graver blanks. grs, riogrande, and gesswein are just a few sources for gravers.