Please be sure to order the correct wind vane for your 6410 anemometer - the cross sectional shape of the wind vane spindle is the key to identifying the correct part.
Wind Vane for 6410 VP2 Anemometer, Round Shaft, no logo. This is for use with 6410 anemometers supplied with VP2 stations prior to revision AF (but is also the correct part for revisions AG and AH).
If you have the 6410 anemometer with the D-shaped spindle for the wind vane (supplied with VP2 stations of AF and AJ onwards revision) then please see item 7906.