"Quality, for generations to come" (we engrave stone).
There's a slight double meaning in the sense that "generations" also means future family members...not just years. We make head stones from family "heirloom" boulders...stuff that's been in the family for a good long time.
Slogan...it's been a while since I've used that word, and from what I've read in my marketing studies, it's now called a USP....Unique Selling Point or Proposition.