The operator of the laser selects the font size of the inscription. Some can be read at 10x and others need 20x or 30x. Strong power loupes can be a challenge trying to read inscriptions, but if the inscription has a black background, it is easier than if the entire inscription is white. Old eye often need a microscope. Use Reflected light rather than Transmitted light whenever possible as such surface lighting makes surface features, such as a laser inscription, higher in relief and more prominent and visible.
I managed to (barely) read the inscription on my .34 and a 10x Loupe by lining up my iPhone 4 camera with the Loupe and then zooming the camera in as far as it could go. So if you're looking to buy a Loupe you might be able to make it work with x10 too, but probably easier if you went with x40
I put my 30X loupe in a drawer about twenty years ago, and have no idea where it might be now.
I just use my trusty microscope dialed up to about 30 to 50 X. Of course, I could buy a couple of half carat diamonds for what that thing would cost me today...