From the photo, it looks like a separate part. I'm no expert, but I've handled more than a few Hi-Powers, and I've never seen anything like this. I'd really like to see more photos when you get the gun. Thanks for pointing this out!
Also, I wouldn't be in a hurry to change anything about this without more information.
Hoot
http://i9.photobucket.com/albums/a82...r/IMG_3502.jpg