Type: String
Identifies class or source of the SecurityAltID (455) value. Required if SecurityAltID is specified.
Valid values:
Same valid values as the SecurityIDSource (22) field
Added in protocol FIX.4.3
See in: FIX.4.3, FIX.5.0, FIX.5.0SP1, FIX.5.0SP2, FIX.5.0SP2 EP240.