Howdy,
Back in the good ol' days of Cowboy Action Shooting, when a scenario might include 12 or 13 rifle targets (Horrors!) instead of the now standard 10, Davidson's ordered a bunch of long-tube M94's that will hold two more rounds than the standard M1894CS. They had standard rifling to work with lead bullets and smooth wood. Later versions offered by Marlin went to a 20" octagonal barrel and checkered wood. Since the majority of cowboy shooters can't handle the idea of shooting more than ten rounds at any bank of targets, the long barrels have fallen out off favor.
You are lucky to have found one in a darned useful caliber. I switched from a short Marlin to a 24" Uberti '73 .44WCF in 1999 after getting tired of loading the last two shots through the side of the Marlin on long stages. 4" of barrel might not seem like much, but it turns a carbine into a rock-steady off-hand gun.
Bitterroot