Depending on your eyes and how much detail you want to see, I use a 2x that is 1 1/4 inches in diameter is quick and easy, and lets me view dates which my eyes have a hard time seeing anymore except in bright sunlight, also comes in a case it slides in and out of and goes well in a pocket. For more detail, like double dies, die cracks and such, a 10 - 16 x loupe is necessary. I was nearsighted till about 45 which changed to farsighted, and just seems to increase every year. Things several hundred yards away are now easy to see, but up close it becomes a nightmare without glasses or a magnifier.