@Acorn The Janome part number for the Even Feed foot that fits their 1600P machine is : 767403016 whereas the Even Feed feet that fit their other sewing machines all have part numbers beginning with 21 or 20. So perhaps there's a significant difference between them.
Hope this helps?
The Janome accessories catalogue also states that 'MC1600P series dies not use standard needles and only those listed ( HL type needles ) should be used.
This catalogue list other extras : concealed zip foot,ditch quilting foot, narrow straight stitch foot, taping foot, ultra glide foot, velvet foot, adjustable zipper foot, 1/4" seam foot, convertible free-motion quilting foot, embroidery/darning foot, narrow straight stitch foot all with part numbers that differ from those for the other sewing machines.