Another Coin Photographer Down The Rabbit Hole.

None of the methods are "wrong", just have different efficacies. You can move the whole camera plus lens, just the camera while keeping lens fixed (using bellows or rear focus helicoid), move just the lens while keeping camera fixed (using bellows or front focus helicoid), or keep the whole setup fixed and move the coin! Each method has its pros and cons and those change depending on the magnification. I remember seeing a table that someone put together that outlined the best method vs different magnifications. I'll see if I can find it.

By the way, excellent work on the SLQ. My only suggestion for improvement is to turn down the EV by 1/3 or 2/3 to eliminate the few blown-out highlights that exist. Here is a pic of those highlights: