Gitzo G1278M Magnesium Ball Head with quick release. Used, but in good condition. Cork pad a bit worn and has crack, but still very usable. Bubble level is fine. Locks up tight (both ball and quick release).
Full specs here: http://www.gitzo.com/product/72038.7...nter_ball_head.
I think this would be fine for MF or field camera; not sure if it's quite heavy enough for a monorail.
$110 plus actual shipping from 56468.