I got my 66-1 back clamp with all it's attachments in a box....I was very lucky and very happy to see them when I got the box!!
But I have gotten tons of various attachments with all the machines I have gotten, and when I got my Davis NVF and all the stuff in boxes and trays from the seamstress's estate, I found lots of feet that go with unknown machines. Some look pretty industrial. One of these days I'll get them all sorted out and take pictures and see who on here needs them or wants them!