Which train is the real ''Orient Express''? Actually it is the one that this year celebrated its centenary. The train, founded in 1883 by Georges Nagelmackers, a Belgian, still leaves Gare de l'Est in Paris every night at 11:15.
With 784 tons behind its electric locomotive, it heads for Strasbourg, France; Stuttgart, Ulm, and Munich, West Germany; Salzburg and Vienna; Budapest; and Curtici and Bucharest, Romania.
The trip takes two days. London-Bucharest return in a single-berth sleeper is (STR)521 ($800), with meals (and spies) extra.
The name ''Orient Express'' remains the property of SCNF French Railways, which allows it to be incorporated into several others.
* The Balt Orient Express, whose red sleeping coaches run within Eastern Europe from East Berlin to Bucharest via Prague and Bratislava, Czechoslovakia; Budapest; and Oradea and Cluj, Romania.
The train is a descendant of the 1898 Berlin-Budapest-Orient-Express, which joined the ''Orient Express'' coaches in Budapest to go on to Turkey.
* The Venice-Simplon-Orient-Express, described in the adjoining article.
* The ''nostalgic Orient Express,'' another restored train, privately owned by Albert Glatt of Intraflug in Zurich.
When Mr. Glatt wishes, his train cruises from Zurich to Istanbul in three days, all meals included. The fare: (STR)2,000 ($3,060), round trip.
The most luxurious of all the trains was the original ''Simplon Orient Express,'' which ran from Calais and Paris to Istanbul from 1919 to 1968 except for the war years.
''Simplon'' is the name of the 12-mile tunnel opened in 1906 to link the Valais area of Switzerland to Italy.
At first the train ran only to Milan, Italy, then to Venice. Constantinople (now Istanbul) was added to help British and French passengers to reach Palestine, Syria, and Lebanon after World War I.
Agatha Christie is said to have written her novel about the Simplon train under the original title ''Murder on the Calais Coach.'' She meant the through sleeper attached to the Simplon train from Istanbul to Calais.
The restored train stops at Venice, not Istanbul. In fact no regularly scheduled West European train goes direct to Turkey anymore.