From the Glenn Woods vcoins.com store:
(Information, description and reference corrected).
 
Carausius, AE antoninianus. London mint. 

IMP C CARAVSIVS PF AVG, radiate, cuirassed bust right.
PAX AVG, Pax standing left holding branch and transverse
sceptre. 
S-P across fields.
Mintmark MLXXI. 

RIC V-2, London 98 var (mintmark for this bust type).

       US$ 255  € 209.44
       £ 142.09
       AUD$ 338.43
       CHF 324.06
       CAD$ 310.64

      Rates for 8/18/2005