Couple of inches down in stubble field.
Gave an 85/6 on the 400i,


Measures 49mm x 14mm, curvature height of 15mm.
Handle slot 30mm x 10mm

Lower slot for blade 44mm x 10mm at widest point

Possible crescent shape pattern front and top of arch.

The rear,

Any further info appreciated, especially the age.
Cheers,

Dave.