I'm using the defaults provided by this site to reduce my pictures, download there and bring up here:
https://www.reduceimages.com/
I just reduce my main window and drag from my camera to the drag point.
Kudos to you for taking the time to check out the equipment. Unfortunately, I don't know much about the industrial machines other than someone will want them, but maybe for less than you would like/dream. From the limited looking I've done, looks like grandma had good taste in her machines!
Here are some overall links you probably already have found
http://www.seiko-sewing.co.jp/en/
https://www.manualslib.com/manual/44...-Ma4-B551.html
https://usblindstitch.com/
There may be surprising value in fabrics, don't discard them without having someone go through them.