Antique locket I got at thrift store for 25 cents

Questions: (1) What are the initials? (2) Is it gold? (3) How old is it?
I imagine it belonged to a woman and the photos are of her husband and baby. It makes me kind of sad that this heirloom ended up at a thrift store sold for 25 cents. However, I'm glad I found it because I will always appreciate the sentimental value of it, even though I have no idea who the people are. Also, based on my completely uneducated guess, I would say it's from the 1880s-1890s.

I removed the photos and here is the mark on the inside, behind the baby photo: