4bf911a6_l_Support___Transaction_fields__Description
[Field Name] nKey [Type] Long [How Used] PKey [Description] 
Unique transaction document record identifier. This is always identical to the nKey of first transaction line belonging to this doc. OfficeQ code artificially generates this key (as well as the nKey for for TranLines). The number used for this key is sequential - in the order the transactions occurred.
DataBlox Technical Support - Transaction fields
Description