The personifications on the reverse
On the reverse, a standing figure holds two attributes, with a word in the legend. These are the personifications: the Roman way of displaying a political programme on an object everyone handles.
The commonest
FORTVNA holds a rudder and a cornucopia: the good fortune of the reign. AEQVITAS carries a balance, symbol of the soundness of the coinage itself. LAETITIA, joy, holds a wreath and an anchor; SPES, hope, walks forward lifting her robe and offering a flower.
VIRTVS appears in military dress, PAX with an olive branch, PROVIDENTIA with a wand and a globe. The vocabulary is stable across three centuries, which makes it easy to learn.
Reading the message
These figures are not ornaments. An emperor who hammers out CONCORDIA MILITVM, the concord of the soldiers, rarely does so because the army is quiet. SECVRITAS and RESTITVTOR ORBIS multiply precisely when the empire is under threat.
That is what makes the coinage of this period so alive: every reverse is a declaration, and the succession of reverses traces a communications policy that no text preserves as completely.
Recognising by eye
Begin with the attributes rather than the legend, which is often partly effaced. A cornucopia together with a rudder: Fortuna. A balance: Aequitas, or Moneta. A modius on the head: the Genius of the Roman People, the commonest reverse of the whole Tetrarchy.