Marc - it IS TRUE that an 1844/1860 can be a conversion of an 1844 Musket, because that is precisely what the dual date means! If I remember correctly; to begin with, the original model in question was a French 1822 model smooth bore flintlock Musket manufactured from 1822 onward till the next model change (can't remember the year of the next French model change). And in the case you mention the 1822 model was manufactured in 1844 as a smooth bore flintlock Musket. You also need to understand that the French licenced two Belgian and one Italian arsenals to manufacture copies of their 1822 model for export. I have owned one each Piedmontese Rifled Musket from the F & T Belgian arsenal, and I still own one from the Italian arsenal in Torin,Italy. The later year designation you mention of 1860 is when two modifications were done to these Belgian & Italian copies of the French 1822 model Musket, and one modification was that the original Flintlock ignition system was converted to the then new Percussion ignition system and the original flintlock smooth bore barrel had the touch hole drilled out, and a rounded bolster welded onto the side of the barrel,over the touch hole and drilled out to accept a nipple to complete the percussion conversion. Next the barrel was rifled with 4 lands & groves, thus the designation "Rifled Musket". So in the example you mention; a Belgian copy of the French model 1822 smooth bore flintlock, manufactured in 1844, was later converted to a Percussion Rifled Musket in 1860, changing the designation to M1844/1860.