It's a great round. It's been around since 1873 and is still one heck of a hunting round. In the Marlin it can be pumped up to "+P" levels by either handloading or by buying some ammo from Cor-bon or several other "high-performance" 45-70 ammo makers. The Marlin lever actions are great guns that have also been around for a very long time. The 45-70 will take any North American game animal you choose to hunt just not at any great distance. For a history lesson check out the following link.....
I've been extremely happy with the Marlin .44 mag I own. Its a pleasure to shoot. I tried a buddies .450 Marlin earlier this year and the mother kicked like a mule. I would imagine that 45-70 would be in the same realm of thumping power. If the price is right I don't think you can go wrong with purchasing it.
If someone offered one to me, I'd take it in a heartbeat. It'll handle anything on this continent.
African guides have been using them, with +Ps, as backup guns, to be used if their client misses the hunted animal, and said animal decides to charge them. Plus, the lever actionallows for a fast second shot.
Dep, I can tell you from experience that the marlin 45 70 is not much fun to shoot off the bench. Its a little on the light side and the stock is mighty narrow for much comfort. I bought one just like yours from a guy who needed some money for a speeding ticket and when I shot it the first time off the bags, I think I almost broke my jaw! Its a fun gun though. I shoot cast bullets in mine more than jacketed. I also put a gold blade on the front and a williams peep on the rear. Fun gun.