Most likely a blade for a timber planer or thicknesser, I'd say. Every chaff cutter knife I've ever seen has been curved.

Someone over at www.woodworkforums.com [an Oz site] may recognise it; some of those folks are into old workshop machinery.

Cheers,
Gadge

"ODK Mods can explain it to you, but they can't understand it for you..."

"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."