PORT LAVACA, Texas—Weapons buffs may stock semiautomatics in the gun safe. But nothing makes a statement like having an Army tank in the garage.

Scattered around the country are members of a small fraternity of guys who own tanks. They are hyper-avid history buffs or hyper-edgy investors or just wealthy men who can now afford hyper-sized versions of the toys they played with when they were boys. Tank brokers—yes, there is such a thing—estimate there are several hundred to 1,000 private tank owners in the U.S.

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