I suggest you try placing the coin in softer light and focusing. Do not use the built in light but place the coin somewhere where the light works for you. Turn the coin around until you get the direction you want. The 12 is not known for good close focus characteristics but no phone takes the best coin pictures. Do not place the coin closer than the minimum focus distance. The camera has enough pixels to allow some cropping but too close always will be fuzzy. The link below discusses ways you can overcome the lack of macro about half way down the page. I have no experience with the accessory lenses and have never (will never) touched an IPhone. Like any other tool, you have to learn to use it. https://iphonephotographyschool.com/focus-tips/ Bottom line: Buy a camera.
Based on your pictures, it looks like the coin is completely silvered. Is that correct? or is that a product of the pictures?
You can always just get a 20x loupe and any cell phone camera will be just fine. Beware of coronal fall-off, but I’m not meticulous enough to care too much. iphone SE with 20x loupe: I use the phones built in editor to decrease brightness between 10-20 and increase vignette to max white.
Very nice photos. The next step is the crop the images. You might also want to place both the obverse and reverse together in a single photo. These are several free programs on the internet that you can use to do this.
Try keeping the iPhone over a stack of books for maximum stability and same-sized obverse and reverse images. You can use the earphones as a remote shutter release: pressing the volume buttons takes a photo. There is a free version of Lightroom on iOS, which allows more advanced editing than what is available in Photos.
Microsoft Paint is my preferred. Use the phones editor to adjust brightness and vignette, then use Paint (preloaded onto all windows computers) to put front and back together.
I process images on my Laptop and combine them using Paint as well. When I have to use the phone/tablet, sites such as this one help: https://www.peko-step.com/en/tool/combine-images.html