The 'For Black Powder' barrel did not come out until 1905. It would be classified as a Curio & Relic. Per BATF&E regulations, your Marlin is NOT an antique. I have posted this same inquiry on another sight but need to verify since I want to sell this and it would be beneficial to know if it is an antique or not. There is a later tang sight mounted which resists my efforts to remove it so I can't see if there is a model number it. There is also a slight wrench mark on the barrel near the receiver so it looks like somebody has changed or attempted to change the barrel which is also marked For Black Powder. It does not look anything like a 1881 or other earlier models and does look like a 1893 - the location of three screws on the right side of the receiver is consistent with pictures of a 1893. It is marked Marlin Safety on the top of the receiver. The seller of the rifle claims it is a 1893 model as it is marked 1893 as the last patent date on the barrel so I wonder how it could have a manufacture date that is earlier than its model number.
The serial number is D8225 and when I try to look it up as to age (here ) it tells me the rifle was made in 1884 but I do have to remove the letter to get it to work - so just 8225. I recently came across a Marlin lever action rifle in 32-40 caliber that has me a bit mystified.
