Andrew Ratner I N MY basement sits what some of my house guests would describe as a paint-flaked wooden chair. To me, it's a treasure: the box seat I took from Yan- kee Stadiumat that ballpark's "final game" 18 years ago. I doubt the final baseball game at Memorial Stadium Sunday will resemble that 1973 season finale before Yan- kee Stadium closed for two years for major renovations. For Orioles fans craving souvenirs, that'll be too bad. ===== My buddies and I left the baU yard in the Bronx that late Sep- tember afternoon carrying a row of blue seats we had wrestled from its concrete pad, and enough out- field turf stuffed in our pockets to sod a small suburban yard. We weren't strong enough to wrestle the row of seats out of the stadium and feared we'd never squeeze it on- to the "El" — the elevated subway — for the trip home. So we returned to get single seats. And like thou- sands of other fans that day, we left not by the escala- tors, but through the bullpen via the outfield. We walked backward so we could relish the view from Di- Maggio's former patrol. Our heist was comparatively modest. One unknown fan got second base. Others peeled down signs and pulled hunks of padding off the outfield wall. The next day's Daily News had a picture of a nun taking some grass. About 10,000 seats were taken in all, according to one estimate after the game, which drew 32,000. I was too young to appreciate the glories of the post-war Yankees and, truth to tell, loved the Mets, not the Bronx Bombers, but for months I had that Yankee Stadium sod on the window-sill of my family's ground- floor apartment, looking like brown dried pasta in empty Cool Whip tubs. A city kid, what did I know about keeping grass alive? But I cherished my prize for a long time, and my memories of that day, unlike any baseball game experience before or since, still haven't withered. Actually, as I recall, the start of that final pre-reno- vation game at Yankee Stadium was a bit frightening. By the third inning of a contest between the Yanks and Detroit that meant nothing to the season's stand- ings, fans around us with all manner of tools began to dismantle the place. When the home team How do you close a stadium?