There have been rumours about a very cool new lens coming to the market for Sony/Nikon/Fuji/etc cameras that has some use for us coin collectors. It's called the AstrHori 85mm f/2.8 TS-E Macro and it is a tilt lens. Some of you may be familiar with tilt-shift lenses that produce the "miniature effect" that makes everything look like a small scale model.
A tilt lens does not have the "shift" capability, so what does it do and how is it useful for us? So let's say you're standing across the road from a building, facing it straight-on, and you focus your camera on the front of the building. The whole front of the building is in focus because it is along the same plane, i.e. perpendicular to the lens. If you then moved to the end of the street and again focussed on the front of the building, you're now viewing the building an angle and only a small part of the building will be in focus.
source: https://snapshot.canon-asia.com/vn/article/eng/what-you-didnt-know-about-the-tilt-function-on-tilt-shift-lenses
A tilt lens helps us with this second perspective. In the diagram below, we are standing at an angle to the face of the building but we want the whole face to be in-focus, not just the parts that are perpendicular to the lens. The "tilt" in the lens allows us to shift that plane of focus so instead of the plane being perpendicular to the lens, the plane is now at an angle running the length of the building face.
source: https://snapshot.canon-asia.com/vn/article/eng/what-you-didnt-know-about-the-tilt-function-on-tilt-shift-lenses
Ok so now to get to the part about how this is useful for us photographing coins. Many of you may notice when photographing or holding your coins that they often look better at a slight angle, where they catch the light just right. Holding them at this angle can also show off the relief of the coin and give someone viewing the photo a better idea about how it would look in-hand. The trouble with this though is that if you photograph the coin when it is tilted, only a small portion of it is in-focus because the surface of the coin is not perpendicular to the camera.
A tilt lens would let us shift that plane of focus so it runs across the whole surface of the tilted coin, meaning we can get the whole coin in-focus even when it is titled away from the camera. This is a really cool feature that may seem trivial at first but is really quite handy. On top of that, this particular lens (the AstrHori) can achieve 1x magnification. Most tilt macro lenses on the market only go up to 0.5x and cost a fortune (see Canon's line of tilt macro lenses). I'm not sure how much this one will cost yet but I suspect it will be a lot cheaper.