Very Beautiful Mantle and love the fireplace insert! Agree with cogar, this was fairly common in older homes late 1890 - early 1900's. So many were destroyed from renovations and now people are beginning to appreciate the simple artistry that is very fashionable today.
Now, the insert is one I have never seen before. Depends on what part of the country you are in where you see a prevalence of the different styles. Very nice, ornate, but not overdone.
I would definitely give it a $1500 as it appears to be in great shape, beautiful appearance and if in perfect working order!