(FORTUNE Magazine) – Easily the strangest federal agency in our country's capital these days is the National Mediation Board. Nobody can explain this animal to us. For openers, nobody can make clear how it has managed to remain totally, unabashedly pro- union after more than eight years of Reaganism. Both members of the board were appointed by Ronald Reagan (a third position is vacant), the guy who made his day by gleefully breaking a strike by the air traffic controllers. But the NMB members and staffers go right on acting as though nothing has changed since Frances Perkins was Secretary of Labor. The board members even had the liberal New York Times calling for their skin a while back, based on their obvious commitment to the Machinists Union, which itself was bent on destroying the Lorenzo regime at Eastern Air Lines. Wait. It's worse than we just said. Something has changed at the board. After 55 years of existence, it has finally discovered Soviet-style elections. Sometime in the next few months, if all goes as now planned, the NMB will conduct its first election under the so-called Key Ballot. The election will determine whether pilots, flight engineers, and flight attendants at Key Airlines wish to be represented by the Teamsters. It works this way. All employees eligible to vote will receive a ballot with one question on it: ''Are you opposed to representation by the International Brotherhood of Teamsters -- Airline Division?'' If you are opposed, you put an X in the box and mail back your ballot. If you are indifferent or out of town or in favor of the Teamsters, your task is easier. You just stand there doing nothing and it counts as a vote for the union. To get beaten, in other words, the Teamsters have to rouse the voters to act affirmatively against them. As demonstrated in the recent Soviet elections to the Congress of People's Deputies, such ballots are not absolutely foolproof. The party boss for the Leningrad region also had no opposition on the ballot, but a majority turned out to vote against him. Still, the Soviet version of the Key Ballot is basically what gave the Communists their majority in the congress. Back to the NMB. It operates under the Railway Labor Act, which was passed in 1926 and made applicable to airlines in 1936. Its two industries operate under totally different rules from the rest of American business, most of which is governed by Taft-Hartley and the bad-enough National Labor Relations Board. One difference between the two systems of regulation is that the NMB is not, even in theory, required to be impartial. Last year a federal court of appeals upheld the board's right to be biased, noting that ''there is no express statutory duty of neutrality.'' Another difference is that the Railway Labor Act, unlike Taft-Hartley, does not explicitly guarantee employer free speech. One of the reasons Key Airlines is now facing Soviet-style elections is that the board is punishing it for reminding flight crew members of the Teamsters' ''sordid reputation.'' The union was badly beaten in an earlier election at Key (which the NMB has set aside), but we gather the company is not too confident of its fate under the new rules. Still, it can hope. There is, after all, the Leningrad precedent.