.5mm play in the door sounds off. Foam may be old/compressed. Peruse all foam and replace before it wanders elsewhere, quite easily costing more in cleaning, repairs and image quality. Appears to be missing the thread-on eyepiece (with rubber coating over the metal ring). There isn't a model number associated with the piece as it is simply known as 'eyepiece for Nikon FE, FE2, FM, FM2n, FM3a'.