That is true for the FM2, FM2n, FE2, FA, and FM3a. Not true for the FM and the FE.
A link showing a pic of an FM body with the button plainly in sight is here: http://www.flickr.com/photos/marcus20/3618725672/
APUG: F3P, F2AS, F, FM2n
Nikkors: 24/2 AI, 43-86/3.5 AI, 55/1.2 AI, 85/1.8 K, 105/4 Micro AIS
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