Many bobbin cases look alike, but there are a few differences worth noting. There were a total of five different stamping sequences used to mark the Singer Featherweight bobbin cases. The number (45750) was consistent through the years, but the order and location of the stamp varied.
Let's begin with the Bobbin Cases made in the USA.
The first stamp was used from the beginning of Featherweight production through the very early 1950s.
The stamp read:
The next stamp was used for just a few years and was marked:
The last US bobbin case was stamped similar in order to the first one, but the lettering was far lower on the bobbin case.
In the UK there were two bobbin cases; both of which were stamped, "Simanco 45750."
The first case had its number on the outside, and it was stamped upside down.
UK 221K and 222K from 1947-1954 Approx.
The final UK bobbin case was stamped on the inside. The case was used on all later Featherweights in the UK including the white 221s.
While each bobbin case had its own era, all original Featherweight bobbin cases are interchangeable. If the bobbin case in your machine happens to be from a different era than the machine itself, no worries; it is better to have a vintage original bobbin case than a replica any day! After all, proper stitch formation is of most importance.
That said, is your machine having trouble with stitch formation? It could be that your Featherweight has a replica bobbin case as opposed to a vintage original bobbin case. Here is a link to our tutorial on troubleshooting stitch problems.