Antique Charcoal Portrait, But What is Approximate Age???

This was a great find today at a sale in a storage facility nearby. I loved the old frame (faux painted tiger wood) & the picture inside was nothing to speak of but I purchased it because it was a such a great buy for just the frame. After getting it home & looking at it closely, the very old cardboard in the back of it had definitely been moved often so I removed it. What I found was this lovely antique charcoal portrait tucked inside behind the not so wonderful picture that was showing in the glass. It has water damage but it's still a very intriguing looking couple from days gone by. It's clearly very old, and on a type of paper that looks similar to wall paper. I also posted a pic of what is written on the back. The portrait itself is approximately 18 inches wide. I only knew it was charcoal because looked at my black finger tips after putting it in so that it was showing in the glass. Can anyone tell me approximately the time period given their clothing or other details? Or any other details to help me know what I have? Thanks so much in advance!