Remington Rolling Block Rifle

[TimOD9857]

Hello All,
I new to this forum so please allow for a few errors. I will try to learn from you all and keep this an enjoyable please to learn, talk and ask questions. I recently purchased what I believe is an 1866/67 Remington 32cal Rolling Block Rifle. It is a single shot breech loading. There is a thumb-activated lever, approximately one inch long on the right side. It sets about ½ way between the trigger and the breech lever. It is toward the wooden forearm. I am not familiar with this. It doesn’t appear to serve any purpose or do anything. Whenever I move it nothing changes. Does anyone out there know what this lever is for, what purpose it serves and how it works? Thank you all in advance for your assistance with my question.
Thanks,
Tim O’D