It’s not like ours is the only horse-and-carriage show out there. We get that. And you won’t find cascades of mint juleps, nor quite the score of UFO-sized flowered hats that populate other grand horsey shows and races. But the Devon Horse Show — the oldest and largest outdoor, multi-breed horse competition in the country — serves up its own unique mix of equestrian glamour, all wrapped in a quaint country-fair atmosphere. It is a grandeur and prestige of a distinctly Philadelphia quality. You find it in the light-blue painted grandstands, the yearly pink geraniums, the inevitable mud that splatters our Lilly sandals as we hike from the car to gobble up teensy sandwiches and the special iced tea blend at the tea cart. After 112 years, the show is constant and steady in a been-around-forever, old Main Line way that makes us feel like we’ve never changed. Even if we have.