Can You Use A Light Ring With A Compound Microscope?

You need to find the objectives that are meant for metallurgical inspection. They often have an "M" in their model number, like M5, or MPlan5, or similar. These typically have enough working distance between the bottom of objective and the subject to bring light in at a reasonable angle. Some of these also have descriptions of "LWD" or "ELWD", Long Working Distance or Extra Long Working Distance. These are especially good for coins, and have plenty of room for lighting.

Some types are also meant specifically for macro work. The B&L Micro Tessars, Zeiss Mikrotars, and similar lines of lenses have RMS threads and are made for systems with interchangeable lenses. These can be excellent for coin photography.

Some bio objectives have long enough working distance to be used with direct lighting. Most likely your scope will come with a 4x, 10x, and then either 20x or 43x, and either 40x or 100x. Only the 4x and possibly the 10x will be useable for coins, and only if they have fairly long working distances. The bio microscope will also have a 10x eyepiece, which you'll need to remove and install an adapter for your camera. You can use the eyepiece but the image quality will suffer, and you'll still need to get a (different) adapter. This assumes the microscope does not have a photo port, which makes it even more complicated...