Flash spotting telescope
I assume that you are talking about a telescope of the type used to spot the flash of enemy artillery in order to determine the location of the enemy battery. I'm sure it's a beautiful piece of high-tech optics if it's in good condition.
Normally flash spotting was only one of the techniques of locating enemy artillery. Flash spotting was used in conjunction with sound ranging, surveying ( observing and measuring enemy shell bursts) and other intelligence sources.
Today, radar performs many of the functions of locating the source of enemy artillery and mortar fire.
You are going to have to locate a military manual describing the use of that piece of equipment. It's a rather technical field and it won't be easy to find.
Otherwise you have a superb optical instrument for nature study.
