The Russians are coming to Middle River, Md. But nobody there can figure out why.

An appendix to the new intermediate-range nuclear forces (INF) treaty lists Martin Marietta Corp.'s Middle River plant, 12 miles east of Baltimore, among 11 U.S. facilities that will be open to periodic visits by Soviet inspectors.

That is fine with Martin Marietta, except for one small point. The Bethesda-based defense firm -- contractor for the Pershing IA and Pershing II missiles that the treaty eliminates -- doesn't make the weapons at Middle River. It makes them at its Orlando, Fla., plant, which is not on the list of inspection sites.

If the Soviets want to come to Middle River, "they won't see any missile launchers. They probably won't see much of anything related to nuclear weapons," said Phil Giaramita, a Martin Marietta spokesman.

"We don't know every twist and turn as to how they {U.S. and Soviet negotiators} made these choices," said Stan Norris, a senior research associate with the Natural Resources Defense Council, an environmental group that has closely monitored the arms treaty and first disclosed the list of inspection sites in the appendix last week.

"Some of it looks logical," he added. "Some of it looks a little weird. Middle River looks a little weird."

Martin Marietta officials are equally perplexed. The idea behind the inspection sites -- there are about 70 in the Soviet Union -- is to ensure that neither side tries to cheat by continuing or restarting production of the banned missiles. Middle River, headquarters of Martin's aero and naval systems division, undoubtedly qualified as a place the Soviets might want to look because it once made the launch carriers for the Army's Pershing IA missiles.

But as company officials are quick to point out, the last Pershing IA launch carriers were made at Middle River 16 years ago. When Martin's updated Pershing II missiles were deployed in the early 1980s, the Army simply modified the existing Pershing IA launchers already in the field in West Germany rather than start up the production lines again at Middle River.

All the company officials who once worked on the Pershing launch carriers have left, the company says. Even the special tooling that Martin Marietta used to make the launchers is gone, and nobody at Middle River can remember where it went.

"As with any institution, people come and go around here -- and there is nobody here today who worked on that program," said Buzz Bartlett, Marietta's director of public relations at Middle River.

"Our facility is over 1 million square feet of factory space and I would be hard pressed to find the area in the plant ... where the launchers were built," he added. "There may be some special tooling we used to make the launch carriers, but we don't have it anymore."

In the meantime, company officials at Middle River are amused by their new-found role in world affairs. The 58-year-old facility was once the flagship plant of Martin Marietta's forerunner, the Glenn L. Martin Co. It employed up to 52,000 people during its heyday in World War II, when it made the B26 "Martin Marauder" bombers, Navy seaplanes and other aircraft.

But as other Martin plants -- particularly in Orlando and Denver -- boomed with large missile and rocket contracts, Middle River faded into the background and was close to being shut down in the late 1970s, according to Bartlett.

It has staged a modest comeback in recent years, landing contracts to produce the vertical launching system for the Aegis cruiser, tail structures for the B1 bomber and thrust reversers for both military and commercial jets. About 4,500 people currently work at Middle River.

What will happen when the Soviets arrive is a matter of conjecture. Late last month, the Pentagon called in Phil Sendel, president of Martin's aero and naval systems division, and Middle River's chief of security to inform them of the plant's new distinction.

But no details about the ground rules for the visits were offered, other than those already made public: The Soviets will have to give advance notification and will be "closely supervised" when they come.

They will also have the right to visit on a periodic basis for the next 13 years.

Is Middle River looking forward to its visits?

"I don't mean to be facetious, but being inspected is not part of our major business thrust," he said. "I'm sure it's going to be an imposition."