Appraisal of Gilbert Regulator #11

The clock has been well maintained. It still has its orignal finish. All origanal glass is intact. The owner asked me along with restoring it to give him an estimated value for insurance. I found it in an old collector book I have from 1983. At that time it was $1250. What can you tell me of it today and where can I find information about how many were actually made of this model? The atached photo is of the case. I have the movement out for servicing. R/ Kris Knue

Good