The Marlin 44 Mag is the Model 1894.....there were some 336's made in 44 Mag years ago but these are extremely rare.
I have a blued 1894 44 Magnum in near mint shape with a Williams reciever sight (these sell for about $80 I think) that I'm selling for $450....
new ones are $560 plus tax. I think the older ones are better, nicer blueing, no cross bolt safety and no checkering.
out to about 100 yards I think the 44 Mag is as effective as the 30-30.