19th Century Mid Shipman's Brass Telescope

This is a nice example of a 19th century brass telescope as used by the Navy mid shipmen, it has three draws and day and night section on the end. It comes in good physical condition given its age but I cant get it to focus, from the bottom end you can see through but the business end has problems, it may be missing a lense or one is out of place so some sympathetic restoration required, it comes in its original leather case and measures 8 inches closed and 25 inches fully extended.