The letters GSA, usually thought to stand for General Services Administration in this government town, could just as well stand for Grand Scale Auctioneer.

When GSA is not buying and maintaining federal office buildings and other government property, it's Uncle Sam's chief auctioneer.

Next month, for example, GSA will hold an auction at its Navy Yard warehouse here to sell to the general public 25 nearly new cars, including 1976 models of the Datsun 280Z and a TR-7, plus 100 typewriters, 40 to 50 adding machines and 200 filing cabinets, desks and chairs.

The agency also has some more unusual merchandise to sell -- 500 to 700 pieces of gold and silver jewelry, including several with small diamonds and emeralds. One piece is appraised at $10,000.

For the nautically inclined customer, GSA is also offering two Coast Guard cutters and a 1920s-vintage buoy tender that are now docked in Baltimore. Just this week. President Carter put the presidential yacht Sequoia on the auction block as part of his frill-cutting campaign. Sale of the 123-ton craft will probably be handled by GSA, a White House spokesman said.

Last year, a Coast Guard ice cutter sold by GSA fetched $240,000 from a scrap dealer who wanted the ship for its metal, according to William Tesh, who runs the Navy Yard warehouse.

If these items don't appeal to you, GSA also has real estate. For instance, in Philadelphia, a 52-year old, 15-story office building that is no longer used by the government is for sale. The building is adjacent to Rittenhouse Square, one of the city's finest downtown locations.

Closer to home, the agency recently sold to area developer William Cafritz an 11-acre tract in Anacostia for $355,000. The land was formerly used to house officers stationed at nearby Bolling Air Force Base.

A 1,200-acre naval training center at Bainbridge, Md., and the entire 330-acre Ft. Holabird Army installation on the outskirts of Baltimore are also for sale.

The general public probably will not have a chance to acquire these two properties because like most surplus government properties, they are usually grabbed by state or local governments for schools and parks, according to R. Carlton Brooks, head of the GSA real estate division for the Washington regional office.

Under GSA procedures, federal agencies and then state and local governments have first crack at surplus property before it is put up for auction to the general public.

The state of Maryland will probably buy the naval center for a future power plant site, and Baltimore has long eyed Ft. Holabird for an industrial park, Brooks said.

GSA is the government's procurement agency. It buys most furnishings and equipment used in government offices across the country along with cars, trucks, tractors, jeeps and other vehicles used by government employees.

When a government agency discards a still usable piece of equipment, it is returned to GSA. The latter asks other federal, state and local government agencies if they are interested in purchasing the item. If they are not, the item is sold to the general public.

To notify the public of real estate and personal property sales, GSA maintains lengthy mailing lists. The mailing list for real estate sales contains almost 15,000 names nationwide and is kept in a computer in Denver, Colo. There are 25,000 to 28,000 names on the mailing list for personal property sales just for the Washington region, which includes Pennsylvania, Maryland, Virginia, West Virginia and the District of Columbia.

Persons wanting to get on the mailing lists can so simply by requesting an application from GSA and specifying the kind of surplus property in which they are interested.

Citizens can request sales announcements for such diverse items as airplanes, boats, books, cameras, clothing, computer and other electronic equipment, livestock, pumps and compressors, Quonset huts and woodworking equipment.

GSA does not sell guns or any kind of military equipment. The Defense Department sells its own surplus equipment, except real estate.

The gold jewelry that goes up for sale next month is unusual even for GSA, which sells just about anything.

"It came to us from Customs through the Smithsonian (Institution), and it's our job to sell it, so that's what we're trying to do," said John Suter, regional director of the personal property division.

The jewelry's history is uncertain. Suter said he thinks the jewelry, which consists mostly of ornate gold settings for pins, rings and bracelets, was ordered by a jeweler while traveling overseas. When the shipment arrived in this country, the jeweler decided to forfeit his purchase because of the high duty charges set by the Customs office, Suter speculated.

"The Smithsonian took them lock, stock and barrel to melt them down," Suter said, but they were left untouched. Recently, when some Smithsonian employees "were cleaning out one of their back vaults," they discovered the jewelry and sent it to GSA, he said.

The collection includes several 14-carat gold pendants, cuff links and bracelets and at least four 22-carat gold bracelets, all with intricate Oriental designs.

Suter said he and Tesh are still trying to determine how to display the jewels for public inspection and yet prevent thefts. All items for auction by the regional office are displayed at the Navy Yard warehouse prior to auction so prospective buyers can browse.

Browsing through the cavernous warehouse is how Walter F. Peterson, 69, of Vienna found his old calculator six months after retiring from government service.

"I was just looking around one day for calculators," the accountant said, "and I saw the calculator I had used. It had my name on it still and I bought it. I paid $70, which was too much, but I wanted it and I wanted to make sure I got it."

Sales of office equipment and furniture are held at the warehouse every other Thursday, while the vehicle sales are conducted the second Wednesday of every month.

Sales of miscellaneous items such as computers and electronic equipment, cameras and hospital supplies are not held on a regular schedule.

All items are tested to assure they are in working order before they are sold.