The twin cities of Nogales, Sonora, and Nogales, Arizona, are hot in autumn, and this story started in the heart of the Mexican twin on a sweaty September day in 1951.

Stop for a minute and let a balding middle-ager recall that once upon a time a hasty shine on his spurworn boots, clean Levis, and a few silver pesos in his pocket were all that was required to enjoy a day and night in that friendly border town, and to relax at the end of a week of far riding on a U.S. Border Patrol broomtail. After cooperating with a slug or two of Jose Cuervo tequila bracketed by salt, I ventured forth this fall day to inspect the action around the big shady plaza.

The only thing moving seemed to be a plump traffic policeman, all brass and starched khaki. I lonesomely aimed toward him, figuring on practicing my Spanish.

All thoughts of linguistic betterment left me when I saw the sixgun at his hip. It was a short-barreled Colt single-action in almost new factory condition.

In my most flowery Tex-Mex I inquired if the officer's sidearm was for sale. It was not. Many turistas had offered him much money for his gun, "but a police official must be armed, senor." Would the Captain (he was a corporal) consider a trade?

His eyes were those of a Spanish conqueror about to loot a Mayan temple. Drawing himself erect and haughtily sucking in his belly, he proclaimed, "It would require a new .38 Special to exchange for my pistol--a new Smith y Wesson."

I reached inside my shirt and handed him my gun so fast he probably thought I was throwing down on him. It was a brand-new Smith Heavy Duty .38-44, topped off with a fifteen-dollar pair of Lew Sanderson's custom grips. No more conversation was necessary. A bargain had been struck.

My prize was a beautifully casehardened and blued Model P Colt in .41 Long Colt caliber--not the best for my law enforcement tasks. But I later rebarreled it to .45 Colt and toted it many a horseback mile, trailing up illegally entered aliens in the Santa Cruz river valley of Arizona. I had hated to lose my big Smith & Wesson .38, but the fatter slug of the .45 I wound up with was much more authoritative. Having cut my teeth on a Colt thumbbuster, I was infinitely more comfortable with the new hogleg and damned grateful to get it.

Everyone knows how tough it was to get single-actions between '41 and '55, when Colt knuckled under and started making them again. It seemed to me at the time that all the well-heeled Fancy Dans in the world were conspiring against me to take every existing Colt Model P out of circulation and hang them on a wall somewhere. My success with the Nogales cop planted a seed in my mind, and a hungry gun hunt began.

My trail led me into Mexico several times a year, and I started making the most of these safaris, asking everyone I could buttonhole if they knew anyone who had an old gun. At first, I was met with suspicion and innocent-eyed avowals that "the people around here don't carry guns, senor." There was a new federal arms registration law in effect. I knew of no one who was complying with it, but to have a stranger come out of the sunset and ask you point blank if you had a gun was a disquieting experience, requiring cautious answers. It took tact, patience, a few funny stories over a bottle of beer, and finally a display of multi-colored Mexican bank notes to get the ball rolling in each new village I hit. But each one yielded up guns. Guns like I had never seen before.