A couple of weeks ago, I passed along a story about a policemen who jumped into "his" unmarked police car at headquarters and drove away - only to discover later that he wasn't driving the car assigned to him.

A reader thereupon noted that the officer who had parked the car at headquarters must have left the keys in it, which is against the law. If the keys were not in the car, the second man couldn't have driven off with the wrong vehicle, the reader said.

John F. Miller was the first of several District Liners to point out that sometimes an automobile key fits more than one lock or ignition.

The "stolen car" story also sent Marion Holland of Chevy Chase to her typewriter. "Something over 50 years ago," she wrote, "my father drove his green Hupmobile to work at the old Department of Agriculture building and parked it, as usual, in the block south of the Mall. That street is gone now, and so are the big trees that shaded it, and the little houses with the iron railings around tidy front yards; something to do with Progress."

A little later that day, Marion had to meet an arriving guest at Union Station. With the spare keys to the Hupmobile in her pocket, she hopped a streetcar and went to the spot where she knew she'd find the car parked. She had always had trouble getting the key to turn in the door lock, so she wasn't surprised when she couldn't get the door open right away.

As train time approached, Marion got into "something of a dither" as the lock continued to defy her.

At that point, "a large, fatherly cop came strolling by and offered to help." But the key wouldn't work for him either, and Marion was getting very nervous.

"Now, now, don't you worry, little girl," the policeman said. "I'll go borrow a screwdriver from a storekeeper down the street and I'll have your car open in a jiffy."

With that, he set off for the corner, and Marion had a few moments in which to look about and notice, for the first time, that another green Hupmobile was parked just a few spaces ahead. Her key fit just fine in that one, and she was gone - fortunately - before the policeman returned. Heaven only knows what thoughts coursed through his head.

What may turn out to be the final word on all this comes from Muriel Raum of Alexandria, who stayed at a large hotel in Miami recently and upon her return sent me an interesting report about keys.

"My vision is not too good," Muriel wrote, so she has developed all sorts of memory techniques to make up for that deficiency. She has become very good at finding her way back to her room, but she's not quite perfect yet.

"One day," she wrote, "the elevator stopped at what I thought was the floor I had called for. I got out and walked down the corridor to where I knew my room would be, unlocked the door, and entered.

"My first thought was, 'They have changed the bedspreads.' Then I realized the room was unoccupied. When I examined the room number, I found that I was in a room two floors below mine."

A day or so later, she again opened the door to what she thought was her room and again found a different decor. "This time I was on the right floor. I had merely overshot the mark and waa in the room next to mine."

It was now time to report these strange events to the desk clerk, but when she did, his only rejoinder was the cryptic statement, "I'm glad you have the key."

Now what was that supposed to mean - that she had been given a master key and the clerk was glad to know it was in honest hands? Or is it really true, as some people say, that hotel keys, like car keys and luggage keys, sometimes open more than one lock?

Says Muriel: "If 'one key fits all,' that certainly would explain the number of hotel burglaries." Yep. That might be (forgive the expression) the key to the problem - especially so because house keys also open locks they aren't supposed to, especially within the same subdivision. A door lock shouldn't be considered anything more than a first line of defense against thievery.