I just received to Maynard rifles and I am having issues IDing them. Looking for some help! The both rifles have the May 27 1851 & Dec 6 1859 patent dates. The first rifle seems to be for a thick rimmed cartridge . No rifling (shotgun?) and has 1873 stamped under the patent dates and 1882 stamped on the opposite side under the Mass Arms info. it has a center fire firing pin and the barrel IDs at .612 at the muzzle and .680 at the breech. Barrel length is 26". Lastly it seems to have filled holes or plugged holes on the top tang behind the hammer. The second rifle seems to be for a thinner rimmed cartridge, shows rifling and is a percussion cap  rifle. Additionally it has a saddle ring on the left side and cleaning/ramrod mount with rod on the right side. Barrel IDs at .504 at the muzzle and .547 at the breech. Barrel length is 20". Any help is appreciated.

The first one sounds like an 1882 model. Don't be confused by the 1873 on the left side near the patent dates. That is the patent date of the cocking lever that brings the hammer to half cock when the gun is opened. That is why it is on the left side with the patent dates. It is not a model designation. The 1882 is the model designation. The rim thickness should be about .070" on an 1882 model. The 1873's used a cartridge with a rim thickness of about .135" and the cartridges are called "thick head" cartridges.

The plugged holes in the tang are for the Maynard tang sight. If your gun was sold as a shotgun the sight was not used and the holes would have been factory plugged.

Many '73's and '82's have mixed serial numbers as the barrels would interchange and now 125 years later many have been swapped out. The second model military guns did not serial number the barrels. If your barrel on the 1882 numbers to the frame you are lucky and it would indicate that your gun was sold as a shotgun.

The second gun sounds like a 2nd model military carbine, but the cleaning/ramrod mount is confusing. Pictures would help a lot. Try to take some and post them.

That does not explain the 1873 marking on the 1882 guns. An 1873 cannot be converted into an 1882 because the breech face is cut back further on the 1873 guns. The barrels are all identical in dimension from the locking lugs to the breech end from the 1st mod percussion thru the 1882 guns except the Hadley device barrels. I've only seen one 1882 without the 1873 stamp on the left side.