  We discuss the impact of finite particle losses associated with instrumental
effects in measurements of moments of produced multiplicities with the Identity
Method towards the evaluation of fluctuation measures such as $\nu_{dyn}$. We
show that the identity method remains applicable provided it is modified to
determine factorial moments $\langle N(N-1)\rangle$, rather than moments
$\langle N^2\rangle$. We further show that $\nu_{dyn}$ remains robust if
detection efficiencies are uniform across the measurement's acceptance. The
robustness is lost, however, if detection efficiencies are momentum dependent,
although the identity methods remains applicable provided detection
efficiencies can be determined with sufficient accuracy.
