It is NOT:
includes/languages/english/meta_tags.php

This file location is a blank template
It does not begin as "blank" unless you edited this - it doe start out by default with "Zen Cart!" and "The Art of eCommerce" which is what I thought I saw on your site earlier....but now it is displaying "Conway's Vintage Treasures" and "Vintage Autographs, Movie Posters and Historical Treasures"

So did you find this?? as you are using the "classic" template - it may be in -

includes/languages/english/classic/meta_tags.php