I found an unusual ambrotype in my family's old summer house. I put it on eBay and immediately got a message from a collector offering me $800. I want to be sure I get fair value for it, as proceeds go toward stabilizing the house. Do any of you have a sense of its value? And please tell me these dogs are only sleeping!

Case is in good shape overall, but there's a bit of plastic missing at one of the clasps. From what I can tell, it's the subject matter that makes this piece unusual.
All information greatly appreciated. IMG_0196.jpgIMG_0212.jpgIMG_0206.jpg