There'll be fuss & feathers flying forever over what the 'sand bar' knife was or looked like. But, we do know what the knife Jim Bowie carried to Texas looked like since he had Noah Smithwick make 10 copies of it to give out as gifts. Afterwards, Smithwick made a living by making copies to sell himself. A friend actually held one in his hands in 1953 when he visited a serious collector, then living in Austin. Briefly, "...the knife had a blade ten & one-half inch long, two inches wide and a quarter-inch thick. The clip or 'gut-tickler' was three inches long and perfectly straight, not dished. The point was at the center-line of the blade. It had neither fuller nor ricasso. Knife folks know that a fuller is the so-called 'blood-groove' in the blade, which has all sorts of fanciful explanations for existing. In fact, it helps stiffen the blade, in exactly the same manner that a T-shaped bar of iron is stiffer than a flat bar. The ricasso is that little piece between the hilt and the blade that isn't sharpened and usually has the knife-maker's trademark on it.
"It had a perfectly straight iron crossguard, a full tang, and a grip made of two pieces of light colored wood-possibly bois d' arc (Osage Orange or 'Hossapple')-which was fastened with two large rivits. The blade was marked near the guard with a large spread eagle and N. SMITHWICK in capital letters in a semicircle over the eagle. The dimensions of the Smithwick Bowie are identical to the dimensions Wellman gave for the Bowie knife in "The Iron Mistress", which leads me to believe that he probably saw and measured a Smithwick Bowie in the research for the book."
The above was from "Texas Tales Your Teacher Never Told Me" by C.F.Eckhardt, who actually measured the knife in 1953. Noah Smithwick gave the size and shape of the knives he made for Bowie in his book "Evolution of a State" which is still in print from The University Of Texas Press.
Like Charley says, at least we know what the knife Bowie carried to Texas looked like.