Here is my update.Not to provoke an argument re 1.55 and 1.35 V batteries and their usage, I just want to tell you of my experience with my 1965 214 Accutron. In its life it probably spent more hours in my sock drawer (put there when the mercury cells ran out). About two years ago I sent it off for a CLA. I asked that it be adjusted for the silver cell voltage. It came back and I found it to be not as accurate as I expected, running slow at the ragged edge of the original Bulova specification. I got used to making the occasional adjustment to satisfy myself. I don't know what prompted my next step but I sent away for five Accucells (I did like the price). Now the watch seems to be dead accurate! My reference is the Apple Watch that I have. Don't laugh, the watch uses the iPhone as a source and the Apple's time base eventually goes back to NIST in Boulder, Colorado. I can't explain it but I'll live with that.
Had to give up on my Accucell, just not enough life. Back to my 1.55 V silvercell (which made it run slow at the ragged edge of the Bulova spec.) and it looks like I should get a year's life. And by running it overnight (when off my wrist) with the "tines downwards" it passes my AppleWatch test consistently during the day usage. Looks like Mother Gravity will have its effect. Back to my long time test. Will keep you posted.