I too was stuck on 'measure/aqueduct' - it was my last entry - but I'm now concerned at an earlier comment:
'I think it's just to guarantee that you've correctly identified them. The particular entry method means that they're all uniquely specified, after all. '
Does 'uniquely specified' imply all different? I have both 38ac/32d and 43ac/14d as WE.
Have I missed something or did the earlier poster mean something different?