Interesting.  Mine has a raised fence, and No "Colt" stamped into the receiver block.  I believe the OEM Bayo lug was ground off.  I modified the rifle to accept an internal, DCM-acceptable tube which had a sling swivel.  I have since bought an appropriate bayo-lugged FSB in case I chose to return it to (near) OEM condition.

Given appropriate ammo, and assuming the user does his part, it is a very accurate rifle.

The reason for the internal tube was that if one took a tight sling, one would definitely bend the HBAR barrel.  The tube, internal to the plastic handguards, eliminated this problem, and also added forward weight to the rifle, which most target-shooters prefer.

The smart user might want to investigate so-called gooseneck mounts which attach to the carry handle, and provide a ow-mounted rail forward of the carry handle.  Your choice of optics, given that almost ideal mounting (and co-witnessing) position is up to you.

I believe ARMS still offers such a mount, and it is well-made.

Even the cheap Chinese carry-handle scopes can be surprisingly effective, although not lifetime reliable.  I have one, and it still shoots to POA after all these years.  Even if it fails, it's still a decent monocular spotting scope.  Extra points if the reticle is illuminated.