If you google 'antique herb chopper' you will get a bewildering array of very unusual designs, some even multi-bladed with two handles, and also a number of very ulu-like designs. I've seen Shona war axes made from herb choppers with a single central semi-circular blade 'tang' like the above. I would suspect that larger bladed ones like the OP's may have been repurposed from such a herb chopper. I also suspect many 'herb' choppers' were repurposed circular saw blades. recycling, old style.
see also
http://www.vikingsword.com/vb/showthread.php?t=24004
I have a modern ss 'alaskan' ulu of smaller proportions that makes an excellent pizza cutter - or herb chopper. It gets used a lot.
Some antique ones from google: