Genuine Nikon memory lock button for the F3, F3 HP, and F3 film cameras. Made by Nikon Japan.   Please note, this is the new style button made to replace the plastic button (long ago discontinued) that became loose after many uses and would easily fall out. Installing this part requires replacing the mechanical shutter release cam with new part 40FB-748-1 and using E-ring S1-00800FA on the new lock button to retain it. Plus, installing these 3 parts requires removal of the front standard/mirror cage assembly or what Nikon calls the front plate assembly part 40FB-FA3-6-1.