This coin is part of the famous coded Eqviti series (see the letter "T" in left field, which is the 5th letter of the EQVITI word struck by the 5th officina, i.e. officina "V"), discovered and first published by Alexander Missong in his articale ‘Gleichartig systemisirte Münzreihen unter Kaiser Probus’ (1873).
There were 6 officinae at the 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 AVG
REVERSE: PAX AVGVSTI = Pax standing left, holding olive-branch and sceptre
BUST TYPE: E1= radiate, cuirassed and helmeted bust left, holding spear and shield
FIELD / EXERGUE MARKS: T/*//VXXI
WEIGHT 3.63g / AXIS: 6h / WIDTH: 21mm
