The caseback is closed anyway. Just make the damn movement reliable and I'll be happy.
Well, then you've got to learn a lot!
the pair of gears on the upper right hand side look pretty Rolex to me and the three gears on the bottom bear no resemblance to an eta.
here's a link to a breakdown of the 3255
http://blog.perpetuelle.com/watches/the-new-rolex-caliber-3255-and-the-new-day-date-40/