Accuracy class 0.5 (0.25 USA)
The Tyco data sheet says it is made to meet the requirements of MIL-S-61B which is the US Defense Department specification for current shunts.  Paragraph 3.5 of that specification states that the voltage drop of the current shunt should be 50 ± 0.3 millivolts when the shunt is carrying its rated current.  Since 0.5% of 50 is 0.25, which is close to 0.3, I assume that the 0.5 in the Tyco data sheet mean the shunt accuracy is 0.5% while the reference to 0.25 USA means that the accuracy is equivalent to 0.25 millivolts (slightly better than the US spec).