Omega 2981-6 front or back load?

I have an Omega cal. 491 that I want to install in a NOS Omega case 2981-6.
The problem is that through the back I can't fit the movement, but through the front it goes and aligns as butter.. (making me think that is a front loader, even if the back comes off as a snap on)

Now, if I install it through the front, how would someone service it in the future since the glass would be pressed in?