Help - Unusual Trachy shaped coin with partial shield??

The photo shows a flat view of the obverse and a slanted view of the reverse to better highlight the possible halo feature on the reverse.  The coin is 23x25 mm and weighs 1.75 g.  Note 3 symbols,  ? X I  on lower right of obverse.

 Rather than  ? X I   

if it is turned upside down 

then it looks like  Ι Χ Σ 

which is 

Thanks, very nice.  What has been bugging me is what looks like a shield on the right side of the reverse.  11th-12th centuries are the Crusades and Byzantine coins were frequently overstruck on existing coins.   Byzantine coin overstruck on Crusader coin???  Do you know of any regional Crusader held areas or even European coins of this period which might feature a shield similar to the portion on the reverse??