I have a black longbed Singer 301A that came in a case. While we were vacationing in Wisconsin we happened upon a tan shortbed 301A with a pretty battered up case. It was headed to the trash but we salvaged it. I have since got it sewing a very nice stitch. Since the case was pretty battered up my DH decided he could do a little repair work so he took my case from the black singer to use as a guide. While he had them sitting on the deep freeze in the garage together, I noticed that one was smaller than the other. Were there different sizes in these cases because I didn't think there was any difference in the size of the machines that were sold in these cases.
Here is a couple of pictures.