It depends on which sight is mounted. Recommend you check the manual and consult your local gunsmith use the link below
Best left to a gunsmith
I believe the serial number is behind or to the rear of the rear sight. you should be able to see serial number without removing sight
To remove the rear sight of a Remington 742 rifle, first ensure the rifle is unloaded and safe to handle. Use a flathead screwdriver to carefully loosen the screws securing the rear sight to the receiver. Once the screws are removed, gently lift the sight off the mounting base. Be cautious not to damage the sight or the receiver during this process.
1. Remove the screw to the rear of the front sight ramp.2. Remove the "blade" from the front sight ramp.3. Remove the screw from the front of the front sight ramp (which was formerly seated under the "blade").
To remove the rear sight from a Marlin Model 75, first ensure the firearm is unloaded and safe to handle. Locate the screws securing the rear sight to the receiver; typically, there are two screws on either side. Use a suitable screwdriver to carefully remove these screws. Once the screws are out, gently lift the rear sight off the dovetail or mounting area.
Best left to a gunsmith
To remove the rear sight from a Hungarian Mosin Nagant, first ensure the rifle is unloaded and safe. Use a small punch or a similar tool to drive out the retaining pin located at the base of the rear sight. Once the pin is removed, gently lift the rear sight off the dovetail base. Be cautious not to damage any surrounding components during this process.
Your eye is the rear sight.
you do for a marlin or mossberg
Pull the cover towards the rear sight and lift upwards.
Use a punch and tap it across the barrel. Its a dove tail joint.
drift out with punch from left to right, muzzle pointed away from you.