My pat answer: it depends.
.
If we are talking about what I would call a standard microscope that has a stage and two to three different objectives, then the instrument is merely serving to magnify an image. There is no measurement/assessment/ or anything that can produce an incorrect error/invalid reading.
Having said that, I would suggest that the optics and many other components of the microscope should be maintained for cleanliness, ease of travel/operations, and proper alignment. Otherwise, users will begin to have problems, complain and be grumpy.
If you move to an optical comparator or some type of measuring microscope, that's different. Then, you are "accepting" a product based on a comparison to a template/measured image, measuring the projected image, etc. Within this device the measuring portions should be calibrated. On the profile projector, I would recommend to verify the proper magnification. Nikon sells a glass scale kit (one small; one large) where the small scale values are magnified, and the large glass scale would measure the accuracy of the magnified image (from the small scale).
If this is an FDA environment, I would assume that each piece of equipment has been qualified at some level anyway, depending on it's use, place in the operation, risk, etc. That qualification (depending on use) would give guidance as to what level of service should be performed.
If you have someone come in and perform the services, not all vendors are the same. Maintenance on a microscope can range from blowing it off with a can of air
, to a full disassemble cleaning/lubing, etc. Obviously a good microscope vendor will take longer (and charge more) the first time, as the equipment probably has not been maintained properly prior to their visit. 
If we are talking about what I would call a standard microscope that has a stage and two to three different objectives, then the instrument is merely serving to magnify an image. There is no measurement/assessment/ or anything that can produce an incorrect error/invalid reading.
Having said that, I would suggest that the optics and many other components of the microscope should be maintained for cleanliness, ease of travel/operations, and proper alignment. Otherwise, users will begin to have problems, complain and be grumpy.
If you move to an optical comparator or some type of measuring microscope, that's different. Then, you are "accepting" a product based on a comparison to a template/measured image, measuring the projected image, etc. Within this device the measuring portions should be calibrated. On the profile projector, I would recommend to verify the proper magnification. Nikon sells a glass scale kit (one small; one large) where the small scale values are magnified, and the large glass scale would measure the accuracy of the magnified image (from the small scale).
If this is an FDA environment, I would assume that each piece of equipment has been qualified at some level anyway, depending on it's use, place in the operation, risk, etc. That qualification (depending on use) would give guidance as to what level of service should be performed.
If you have someone come in and perform the services, not all vendors are the same. Maintenance on a microscope can range from blowing it off with a can of air