When discussing details for any coin, which side is left or right? When looking at a coin, it's left side (to our view) is the coin itself's right side. This is driving me nuts when describing a coin.
I agree with @masterswimmer above. In the numismatic literature, I always see references to "clock face" (e.g. "...at the 8 o'clock position near the rim on the obverse one finds the privy mark of the Paris Mint..."). Also, if referring to the "right" or "left" of a device on the coin, I've also read things like, "...the eagle's right talons clutch a globe, while the left talons grip a sheathed sword..."
Clock face terms are more precise, but normally I see coins described from the viewer's point of view, so that "head left" means the head of Athena or whoever is facing to my left as I look at the coin.
Convention is the observer's POV., unless otherwise specified. Also, clock face convention is, for example, K10 for ten o'clock.
You can also use port and starboard. And "bite me" for any objections. RPM's use N, S, E, W or NW etc. to describe the position shift of the repuch. They're kind a small for a clock position.
Okay . . . not trying to confuse anyone, but I shift gears between methods . . . a lot! When referencing the rim I always use clock position. I also frequently use clock position when describing the orientation of die polish or rolling marks . . . parallel with a line running from 11:00 to 4:00. For stars, I reference them by number, counting clockwise from first to last. In the legend I reference the letter in the word, such as second S in STATES. In reference to the devices I usually try to cite specific features of the devices . . . Miss Liberty's left forearm or the eagle's right talons as examples when the possessive case applies. When the possessive case doesn't apply to the devices, as with inanimate objects like the Lincoln Memorial or Monticello, I refer to the features from my perspective . . . right end of steps on the memorial, or bottom step of Monticello. Concerning the fields between the devices and the rim, I usually try to describe the location as being some distance between one of the above and a clock position. So much for keeping things simple. Why do I do this? It's mainly to be able to pinpoint almost exactly where someone should be looking for some detail that is less than obvious. I certainly can't expect others to go to such lengths, but I'm hopeful it helps when someone else can't see what I do, and wants more to go on.
All very good answers. I'll start using the clock method in the future. Then there is zero confusion.