As far the Masonic signet rings are concerned, ideally there is no right or wrong finger or right or wrong hand to wear them. They can be worn on any hand or any finger depending on the owners wish. It has been observed that most married men wear them on the opposite hand from which they wear a wedding ring. Pliny (23/4-79 CE) cited that the fashion of wearing signet rings eventually shifted from being worn on a ring finger to the little finger at that time. Even today most of the people usually wear it on their 3rd finger on the little finger.
Historically the Masonic Signet Rings were supposed to be worn showing the symbol or the engraving in the outward direction showing the “Seal of Authenticity” as a Master Mason. In the earlier times when these rings were also used as a seal, the direction in which the ring was worn was important because the 3D impressions of the same were used in the seals. However now a days since there is no such function associated with them therefore they can be wore in any direction, either showing the symbol or the engraving towards oneself, (so as to remind the motto or the obligation more often) or showing the symbol or engraving towards others.