IHC or ???

[musketjon]

The bottom TG is an IHC--notice the dimple in the end of the locking lug. What is the top TG?? Notice that it isn't dimpled but rather the end of the lug is concave. It is even all around and the other side is exactly the same. Is it an IHC of some-sort or what?
Thanks
Jon
http://i660.photobucket.com/albums/uu321/musketjon/IMG_0001-1.jpg

[Orlando]

Thats a new one on me, dont think I have ever saw one like it

[melloman]

Maybe it is a commercial piece from SAI?