Postumus SALVS EXERCITI error

[Victor]

This coin of Postumus looks like RIC 327 except the reverse legend ends in an S. So the legend is either EXERCITIS or perhaps EXERCITVS. The question is whether this was just an error or should it be a different RIC number. I am leaning towards it just being an error.

The first coin below is the one in question, the second coin is the normal type.

Postumus
A.D. 260- 268
21mm   2.8gm
IMP C POSTVMVS PF AVG, radiate, draped, cuirassed bust right
SALVS EXERCITIS, Aesculapius standing facing, head left, leaning on serpent-entwined staff
Cf RIC V-II Cologne 327