Very rare and desirable legend with INVICTVS (invincible) title. Aurelian was the first Roman emperor to introduce the INVICTVS title in regular coinage. Probus later borrowed this title and used it quite frequently in his own coinage.
THIS COIN IS PART OF THE CODED EQVITI SERIES (see the letter "I" in right field which is the 6th lettter in the 6-letter EQVITI phrase. This coin was struck by the 6th officina, i.e. officina "VI"; there were 6 officinae at Ticinum mint at that time; each one struck a different reverse with a different letter from the EQVITI code). For more information about the (A)EQVITI series see the below excellent article by Gert Boersema:
http://www.oudgeld.com/webbib/translation_codewords.htm
OBVERSE: VIRTVS PROBI INVICTI AVG
REVERSE: SECVRIT PERP = Securitas standing left, leaning on column, legs crossed, hand raised to head
BUST TYPE: E1 = radiate, cuirassed and helmeted bust left, holding spear and shield
FIELD / EXERGUE MARKS: -/I//VIXXI
WEIGHT 3.44g / AXIS: 12h / WIDTH 22-23mm
