Gear will tell you what 'Class' and 'Job' can equip it.

As for multi-class gear:
MRD - VIT/PARRY
GLD - STR/VIT
LNC/PGL - STR/DEX
ARC - DEX/PIE
THM/ACN - INT/PIE
CNJ - MND/PIE
Shields with INT are meant for THM/BLM, MND for CNJ/WHM.