Toastmaster S-131
This is a late 1950s toaster. You can see it featured in a fall, 1958 Life magazine at http://books.google.com/books?id=cj8EAAAAMBAJ&pg=PA74
You are correct that it used the same postwar 2-piece shell, with top seam, as the incredibly popular 1B14 (1947-1961) with the curved...