Definitely manual! An automatic battery will turn on in your pocket or purse if you go in a bar, concert, or a loud buss passes by. Loud sounds will vibrate the sensitive breath activated contacts. The The only safe way to go out in public with an auto batt is to unscrew it from the atty.
I'm thinking the 307 is the auto version of the 306 manual battery. It is
thread compatible with 510 attys.