The patina doesn't look right (to me) for being over 100 years old.
If it is in fact 100% original it should bring a pretty penny.
By the pictures , I am guessing it has been refinished.
The rear sight is a Hepburn sight and could be ordered for all Marlins in that time 1903-1920
I would say if the gun has the original nickel finish after 100 years you see some tarnish on it. Maybe it had good storage. That is one nice Marlin
Looks like one fine rifle to me. I am betting even refinished it would bring north of 1k. Book value might be lower but if someone wants it they are not going to care about the book value. If the pictures show it well and the bore is good I might come off 1k for a rifle like that on the right day. If it is a true original then no telling what someone might pay for it but up close to 2 grand I am sure.
It went into storage when he got out of the service at age 20. About 1950. It was stored in the canvas case. Also, the case has a serial number on it plus marked "92"
Even if it was put in storage in 1950 it would still have been around for 38 years or so.
It just looks to good to have been around that long.
This is just my professional opinion coming from a non professional.
The only way to be sure is to take it to a real professional and have them give you their opinion.
That is if you can find a true professional and not just someone saying they are so they can take advantage.
It is defiantly a nice gun either way.
That doesn't look like a 100 year old finish on the wood either. However that is one fine looking rifle.
Not responsible for what people think, just what I am.
I would consult a Marlin expert that deals in factory engraved Marlins. It is the only way to know, some of the engraved ones sell for 15 times that of a regular catalog model, and yours may be in that class. It would not leave my ownership while I was living though.
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