For general information, go to Google Search, type into the Search Box the words: Moving-coil shell armature DC servo motor. (I have bvolded them so you may clearly see the words.
Now you have plenty of general information about the general question.
SPECIFIC INFORMATION:
Should you need specific information about a particular motor, contact the local supplier, or agents for the makers, quoting Make, Model, Type, Serial Number and whatever else is on the actual motor nameplate.
Trust that assists you.
Kind Regards....
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