The Marlin M1895 Cowboy .45-70is different from your older model M1895 with straight grip stock as follows:
1. M1895CB has 26" tapered octagon barrel with 8-groove "Ballard type" rifling instead of "Microgroove" rifling for easier cast bullet accuracy.
2. Full-length magazine tube for 9 round capacity instead of 3/4 length tube with 4 round capacity.
3. Marble's semi-buckhorn rear sight with blade post front.
The receivers are the same, and both variants can take the full range of Winchester M1886 level loads. The CB special is different from the standard production M1895 in that the finger lever and grip is slightly curved, giving a "pistol" grip. The Cowboy editions started as limited production to cater to the Cowboy Action Shooters, and are now a regular production item because of the high demand.
The longer, heavier barrel has an improved sighting radius, and should be more accurate. Mine and others have reported excellent accuracy.
HTH
John