Yea, thats all I find as well, wondering if it was stamped wrong.
It's not stamped wrong. S-11 was their model number for a 1/2-inch drive ratchet with a longer handle, regardless of the handle style. Everything else except the OAL is identical to the S-10.
Herbrand catalogs can be confusing and don't always represent production.
If you look in Catalog No. 52-M (copyrighted 1940), you will see no M-10 ratchet, the J-10 and S-10 ratchets with the flat paneled handle, and no S-11 ratchet.
If you look in Catalog No. 53-M (copyrighted 1941), you will see the M-10, J-10, S-10, and S-11 ratchets all with that new, ergonomic, pre-bullet handle style.
If you look in Catalog No. 53 (copyrighted 1945), you will see no M-10, the J-10 and S-10 with the flat, paneled handle (prewar style!), and the S-11 with the new ergonomic pre-bullet handle.
If you look in Catalog No. 54 (copyrighted 1948), you will see the M-10, J-10, S-10, and S-11 ratchets all with the new bullet handles.
If you look in Catalog No. 54-M (titled "Revised October 1949," but copyrighted 1947), you will see the M-10, J10-, and S-11 with the ergonomic pre-bullet handle style, but the S-10 with the flat, paneled prewar style handle.