It is a very thin 6.75mm, whereas  the  watches w/  battery  access were  11mm.  1977 was the  year Seiko made  early quartzes  that didn't  have  model names,  just  their quartz  logo  and  known by the  caliber of  the  quartz. This has  the  rare 7830  5  jewel. The  Lord  Quartz  and  the  Chronos came  out  in  1977,  though  the  quartz  logo  of  the  Chronos  would  disappear.
 
Questions & RETURNS: Please Contact or Message  the  seller first and will accomodate your return as a Free Return. Please Avoid opening  a  Case  which happens when a Return is requested thru EBay without contacting the  seller  first. Thanks for  Understanding.


  
Pls. note  that  watches  built  as  water-resistant  or  waterproof are  only  so  when  bought  new.  Water,  specially  steam  from  a  shower  will  enter  these  watches  when  exposed as  the  seller  is  not  a  professional watchmaker..  They  can  only  at  best repel  light  rain  and  washing  chores,  thus  are prone  to  water  damage.