Antoninianus - Probus helmeted, left, spear, shield; VICTORIAE AVG; Victory

(en) About RIC 797
The original RIC text mentions 4 different variations/different bust types (bust types according to Pierre Bastiens grouping of bust types) and there are also two variants known:
[1] radiate, cuirassed, right (bust type B), Numista N# 293153 ;
[2] helmeted, radiate, cuirassed, left, holding spear in right hand and shield in left hand (bust type E1) (Alföldi 089.003), Numista N# 293841 (this coin);
[3] radiate, wearing imperial mantle, left, holding scepter surmounted by eagle in right hand (bust type H2) (Probuscoins.fr #3331 and #4161) (Alföldi 089.001-002), Numista N# 293842 ;
[4] radiate, cuirassed, left, holding spear in right hand and shield in left hand (bust type F) (Alföldi 089.002u), Numista N# 293843 ;
[5] [var] radiate, cuirassed, left, holding spear in right hand (bust type F5);
[6] [var] radiate, cuirassed, left (bust type B2) (example: Probuscoins.fr #91).

Only the 2nd, 3rd and 4th variation are also listed by Alföldi (Andreas Alföldi, Vorarbeiten zu einem Corpus der in Siscia geprägten römischen Kaisermünzen. Heft V. Verzeichnis der Antoniniane des Kaisers Probus, Budapest, 1939, 88).

The emission/year
Probuscoins.fr and Probvs.net list RIC 795, RIC 796, RIC 797 (only on Probuscoins.fr) and RIC 798 as part of the 4th emission of Siscia (year 277), it seems with reference to Karl Pink, Der Aufbau der römischen Münzprägung in der Kaiserzeit VI/I, Wien, 1949. However, Pink does not mention the biga (two-horse chariot) for Siscia at all. He does mention the quadriga (four-horse chariot), with VICTORIAE AVG. According to Pink, the way the exergue marks in these RIC entries are depicted (for example 'XXIP' for the 1st officina) is common for the 4th emission, but also in the 5th (year 278) and 6th emission (year 279). Therefore, it seems also possible that RIC 797 was part of the 5th or 6th emission, which is then also true for RIC 795, RIC 796 and RIC 798.