Singer 78-3

[Zol]

...actually, only precice Singer source says "alternating presser" ,not "walking foot"

so, same as my Singer 15-39, differences are:

- 15-39 is the backside foot the pulling one, jumping after pull forward, while 78-3 front foot is pulling in a circle move.

- 15-39 has feed dog (single line, as also for leather), no needle feed (see pic)

 

Now here is the question (or are the questions):

What exactly is the difference of walking foot and alternating presser? I have here two "Singer walking foot attachments", having an inner and an outer foot.

But I am not shure about that.
My Singer 29 (long freearm shoemaker) has, what I would call a walking foot,
(pulling after stitch back, when needle entered cloth/leather, it's going up and in ordinary position)

Also Singer 16 KSV 11 has a single foot, but some do not call it walking foot.

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Does anybody have a picture of Singer 78-3 (maybe also other do it) from backside? 
My machine has close to presser lever a loose plate with 2 holes at upper end.

Ok, machine lies flat on ground, I forgot to rotate the image to normal stand