Daniel:
I have several sets of S&W pre war grip adapters (a couple of K-frame ones and a couple of N-Frame ones). I believe that those have been modified in that they have the front "arm" removed. I have seen several sets that were so modified and I think that if you look closely that you will see the area that was removed. However, I do agree with Oyeboteb in that whoever modified the GA's did so to have a wider grip.
Here is a photo of one of my N-Frame Adapters. Note that the Patent No is the same as yours:
