This type of mirror shows up fairly often, and is one of the styles that are not particularly popular, but that I would like to know more about. It is common to find them with either this type of crude eglomise panel, or with the "dotted line" outlined paintings, but not usually with something sophisticated. Some people refer to these cruder eglomise works as "gilder's glasses, where the line etching is not well done.
For this one, it looks as if the craftsperson found three separate images of buildings, and used them to fill the space. These motifs of cottages and castle towers show up frequently in mirror panels, and probably had their origins in prints of the period (they do resemble some of the images seen on Staffordshire dinnerwares of the period).
I will be using this design for a replacement panel in a related mirror. I may also replace this damaged one, but am reluctant to do so since it is not particularly attractive in its current proportions.
My version of this panel is below. The green color was interesting; I don't know if it was originally blue and had changed over the years, but I elected to use it in my version, as it was what drew me to the original in the first place.
I adjusted the composition a bit, as the mirror my version went into had less height available for the panel, and I actually think it looks less awkward than it does in the original size.