can you help identify an old black powder rifle?

supposed to be German, model 1842. It is marked as follows: On lock plate behind hammer, in scroll, a large "M" with a small "re"( lower case) even with top of the M then a large scrolled "N" with a lower case "le" even with the top of the N below that is lower case scrolled "de" followed by a large scrolled "M" and the rest is worn off. just behind the hammer is a small oval with a 3 pointed crown and a letter G in it.on the barrel in front of the nipple is the serial number (low 1000) in front of that is a diamond shape with an H in it. Below that is a large MN stamped in the barrel. on the tang area, behind the fixed rear site is a large scrolled M and the lower case le then "1842" then a large screw head then a scrolled (possibly) T. on the left side of the barrel opposite the nipple is an oval with a "M" and a small symbol over it inside the oval. Behind that is another oval with an "S" with another symbol over it inside the oval. The barrel has three bands and is 40 1/8 "inches