There are two hooks that I can think of that it might be. One is the Partridge CS27GRS. It has a small bump like you are talking about. But the one I feel you have is the Mustad 3257B
Mustad 3257B- It is Discontinued the book says. You might find some if you look hard.
The Partridge CS27GRS may be still being made? You can find out if you get a hold of Mustad. They now own that company. Good Luck. Ron