This is a VERY GOOD+ to NEAR FINE condition example of what is technically the US Model 1827 Socket Bayonet. The Model 1827 socket bayonet was an improved version of the earlier Model 1822, which was the improved Model 1816 socket bayonet. While all three of these bayonets look very similar and often not distinguishable without the use of calipers, to the US Ordnance Department they were all separate bayonet patterns. The Model 1822 was an attempt to make the Model 1816 bayonet more standardized in terms of dimensions and in its ability to interchange on US Model 1816 and Model 1822 muskets. The Model 1827 is identifiable by the increased diameter of the neck (or shank) of the bayonet, which was done in an effort to increase the strength of the blade to socket junction. Those bayonets that conform to the Model 1822 pattern but with a neck diameter of more than .450” are officially Model 1827 bayonets. This bayonet has that larger neck diameter which means it is officially a Model 1827. 

It is not immediately clear if this bayonet was produced at the Harpers Ferry Armory or the Springfield Armory between the years of 1827-1831. The years from 1821-1831 were the National Armory Brown period, during which time both muskets and bayonets were finished with a rich lacquer brown instead of being polished to “National Armory Bright”. The face of the blade is marked US / J?. The second letter is not visible. According to the research published by Mark Rentschler, at least eight different “J?” initials have been noted on the blades of 1816 pattern bayonets, including JA, JB, JL, JM and JN found on armory produced bayonets and JE, JH and JR found on contractor produced bayonets. There is also  a small deeply struck touch mark on the face of the blade at the shank junction, that I do not recognize. As this bayonet also has an alphanumeric rack or serial number on the socket, we know it was produced at either Harpers Ferry or Springfield.

The right side of the socket of the bayonet, forward of the T-mortise, is marked with the alphanumeric rack number R/b 84 , a mating number to match it to the musket to which it had been fit. These unique mating codes were also a primitive form of serial numbers, as the use of both a capital and a lowercase letter in conjunction with a number from 0-99 allowed the guns and bayonets to be numbered into the thousands without using long numbers. 

The bayonet remains in about  VERY GOOD+ to NEAR FINE overall condition. This nice example of a bayonet from the National Armory Brown period retains about 40%+ of its thinning and fading original lacquer brown finish, which has worn with age and use. The areas where the finish was worn or faded have developed a moderately oxidized brownish patina, making the bayonet appear to retain more finish than it really does. There is a little bit of old paint residue on the face of the bayonet’s shank. The bayonet is full-length with a 16” blade and the traditional “prow point” associated with this pattern of bayonet. It has a reasonably round socket that does have a small ding on the upper front edge that does not appear that it will affect the ability of the bayonet to mount on a musket with an appropriately sized muzzle. The muzzle diameter is nominally .824”, slightly tighter than the nominal .83” that was designated for the bayonets, but these slightly tighter muzzle diameters are typically associated with later production bayonets. 1816 pattern bayonets are not interchangeable because the manufacturing tolerances of the period simply did not allow that kind of precision in manufacturing of parts on that scale. The blade remains mostly smooth, except for some very lightly scattered areas of minor surface oxidation and equally minor roughness. The socket shows some scattered areas of minor oxidized freckling, as well as some minor impact marks which are most obvious around the neck of the bayonet, as well as the socket lip ding that has already been mentioned.

Overall, this is a very nice example of a later production National Arsenal Brown era US Model 1827 Socket Bayonet that retains some of its original browned finish. These bayonets are rather scarce, especially with this much of their brown finish remaining. This bayonet would be a great addition to you National Armory Brown US Model 1822 (M1816 Type II) or Model 1828 (M1816 Type III) musket, particularly a US arsenal produce example.