Everything from formal furniture to jewelry, dolls and decorator items will be on sale at the 10th D.C. Antiques Fair at the Armory, Friday and Saturday, noon to 9; Sunday noon to 6. Admission is $3.50 for all three days; children under 14 get in free. You can take Metrorail's Orange or Blue Line to the Stadium-Armory station. Call 547-9215. And if you can't find it at the antique show, try the Capital Collectibles Club show and sale on Sunday from 11 to 4 at Armory Place in Silver Spring. This once-a-year swap features steins, figurines, postcards and plates, to name only a few of the collectibles. Admission and parking are free. Armory Place is at 925 Wayne Avenue, one block off Georgia Avenue and two blocks from the Silver Spring Metro station. Call 384-9242. Or, if guns are your thing, you can check out an antique gun show in Baltimore at the 5th Regiment Armory, Saturday 10 to 6 and Sunday 9 to 4. Collectors can buy, sell or trade on guns and ammunition dating back to the Revolutionary War. Homemade soup and sandwiches will be sold. To get there, take I-95 to U.S. 395 (north) downtown, exit at Harbor City Boulevard and drive through to Howard Street.