Closest I can figure after years of study this, in my opinion is the closest thing to what Bowie carried and used. This is a copy of the much fancier version by Danial Serles that Rezin Bowie had made and presented to an important person, and which supposedly was like the one he had made that He gave to his brother Jim. Take "old Bowie, he never snaps" he said or something similar going from memory. Snapping is referring to what occurred in his last fight where the percussion cap failed to ignition almost costing him his life.
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This is how Rezin described the knife he gave James.
original Bowie knife was like a butcher knife in profile, with a thin blade but no silver mounts. Bowie wore it in a silver-mounted black-leather sheath. The Bowie knife gained widespread notoriety after the celebrated Sandbar Fight on September 19, 1827, near Natchez. O
You will notice the blade and handle profile are very kitchen knifish.
In my opinion the knife we know colloquially as the Bowie knife, with huge bkade and sharpend clip and doudle tined guard came along later. Quite probably by Bowie himself to keep up with the growing legend of the blade. It had to get larger and more impressive. There were even schools around the country which taught Bowie knife fighting.
Here you see a copy of the Musso bowie, one of what some consider a contender for the actual Alamo bowie. It is something very like this that I believe Bowie carried into the Alamo.
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Here is the Bart Moore bowie, another knife which sone have claimed as the Alamo bowie.
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Just an opinion.