You have a very unusual cased Accuquartz watch. I have the exact same watch. The case takes a special steel insert into which the movement is set. There is an o-ring gasket under the steel insert as well as a flat gasket under the case back. It really isn't necessary to close up the watch to make it run after installing a new battery but it is good to at least snug up the back so the movement is covered and protected. If the watch has not run in many years, the lube oil may be stiff. A slight, gentle tap of the side of the case at the 9 o'clock position to a counter top may persuade the tuning fork to vibrate. BTW, the stepped side of the battery must face up in an Accutron, unlike other battery operated watches. If the fork does not starrt to hum after a few taps, it will most likely need service. The Accuquartz movement is different from all other Accutron movements and most watchmakers who work on Accutrons won't work on the Accuquartz. I use a watchmaker in Bulgaria who has all parts and equipment to service tha movement. Again, that case is rare for an Accutron. It is large and heavy as are more modern watches. Gold plating of 20 microns is reasonably thick but not the thickest used. Let me know if you have other questions.