A sideways rhombus with a dot in the middle would still make use of all the interpretations offered for the ⟐ symbol. It can be found ready-made without being prohibitively expensive, but it isn't a common fashion item in and of itself. This makes it more distinct, ensuring those who use it are much more likely to do so because of this particular meaning. The two products I linked to are more feminine, but I think with different styling, it would work equally for men. It is more reminiscent of an eye than the ⟐ symbol with 90° angles, giving more weight to the interpretation: "Sic fac omnia tamquam spectet Epicurus." In effect, benevolently saying some thing like: "I might not be the Hegemon in the flesh, and I might not be a fully-fledged bust of him, but I am one of his eyes, and I am – figuratively, metaphorically – watching the actions of the wearer, such that they might find it easier to act wisely," invoking (figuratively/metaphorically/psychologically/subjectively) a sense of a benevolent presence, if you will, without losing any of the other interpretations: the atom, the void, the four lines of the tetrapharmakos, and all the other things which have already been mentioned early on in this thread.
Correct me if I'm wrong, but isn't their reference to Epicureans in particular going around with Epicurus face on rings, cups, etc, as if it's an idiosyncrasy of the school?
And because this variant of a sideways rhombus would entail a stylised aspect of the bust / face, it would connect to the historical tradition of showing the bust / face.
I think it really hits that sweet spot between being a simple geometric shape, yet still carrying meaning through symbolism; and between being very recognisable and very inconspicuous at that same time ![]()
The same holds true for rings: While it can be found incorporated into a rings in a number of ways, it is far less common to find a rhombus with the sides pointing left-right to the neighbouring fingers (see picture below). (In contrast, rings with squares that have a stone set in the middle are quite common, and so is a rhombus pointing to the fingertip / knuckles; so they would be much more likely to just be intended as general fashion items.)