Honorius, AR siliqua. AD 410-423. Rome. 15 mm.

DN HONORI-VS PF AVG, pearl diademed, draped, cuirassed bust right.
VRBS-ROMA, Roma seated left on cuirass, holding Victory on globe and inverted spear. Mintmark RMPS.

RIC X 1353; RSC 70a. 
Rated R5, EXTREMELY RARE.

Although the name of the emperor is not fully legible, the 
visible letters ..ORI.. and the break -VS PF AVG limit this 
coin to Honorius or Arcadius. 
Now we can use the reverse legend and this particular 
reverse type (Roma on cuirass) and, above all, the mintmark 
to pin it down. 
One can see the top parts of four letters:
R or P / M or N / P or R and S or O. 
For this reverse type, Arcadius used only TRPS (Trier)
and LVGPS (Lyons).
For this reverse type, Honorius used RVPS (Ravenna) and - voilą ! - RMPS (Rome).

Contributed by Robert Kopp, Feb. 2015.