Its a percussion .54 caliber smoothbore pistol. The manufacturer was Robert Johnson of Middletown, CT. Eventually, about 41000 of the 1836 Model U.S. Army Pistols were made over an eight year period by Johnson and by Asa Waters of Milbury, MA. In the 1850s, some were converted from the original flintlocks to percussion models. Some of these were used in the Civil War.
I don't believe so. Bamanut's pistol shown in the picture above seems to have undergone a similar type of conversion method to the A. Waters model seen here:
Waters Single Shot Percussion Pistols (the bottom one of the three pictured here shows the: "French" type conversion, while I think that Bamanut's pictured above has the: "Belgium" type conversion). The pictures and explanations are quite good.