Refield Aperture sigt

[McShooter]

I recently bought an old Remington 513T that has a Redfield Aperture/Globe sight system on it. If anyone has any info on these systems I would greatly appreciate it. The sight has sat for so long that it is stuck currently. I believe the grease/oil on it has turned to resin and has it stuck. Any ideas or proven methods for dissasemble cleaning re-assemble would help. Thanks.