This coin has S-P across the reverse fields; but the P has what looks like it may have been an F. The S-F series was before this one. Maybe the engraver just made a slight modification to the die so that he could keep using it. So technically, this coin is RIC VII London 46/56
Constantine I
A.D. 314
Ӕ nummus 19x21mm 2.7g
CONSTANTINVS P AVG; laureate and cuirassed bust right.
SOLI INVICTO COMITI; Sol rad., stg. l., raising r. hand, globe in l., chlamys across l. shoulder; across fields S-P.
in ex. MLN
RIC VII London 56; LMCC 8.06.010