Here's something similar at the bottom of the page:
http://www.kelsew.info/Domestic/dome...lsnolinks.html
Some differences but the Willard stencil appears the same. Probably late Teens or Twenties on the date. Standard 15x1. 2020, HAx1, 130/705H on the needle. You are correct, it is somewhat similar to the Singer 127. I have a later Minnesota E which is very similar to yours that uses a National shuttle and bobbin though it's not made by National. Domestic was absorbed by White in the mid twenties. Not sure what parts are missing but take a pic of the shuttle if your looking for more bobbins.
Jon