I had learned about the "oops" box here and thought it would be a good place to ask about the stamp on the bottom. I'm wondering if it was associated with a particular machine and/or time period. I know the boxes are often separated from the machines, as mine is. I suppose, too, that like blackside singer attachments and parts could have gone with different machines over a number of years.
Janey - Neat people never make the exciting discoveries I do.