I know this is kind of old, but I joined looking for info on this gun myself.
I had wanted one for years, and finally found one in darn near NIB condition a few weeks ago. A really nice little rifle. I've fired about a half a box of ammo through it, just at targets of opportunity out back. Good little shooter. I had it's big brother, a M-66 SuperSingle 20 ga, my first gun ever. Still have it actually, but it's in my sons gun safe right now.
I was wondering when this one was made. The S/N is 135XXX. I've been told that means after '68 since before that manufacturers weren't required to put S/N's on 22's and such. However, I know I got my M-66 in 1966 or '67 for Christmas, and it has a S/N.
Anyway, here's what a M-49 looks like in case anyone hasn't seen one. I added the Ruger Bearcat to the picture to make a 12 year old kids "dream rig from when I was a kid. Man I would have been in "high cotton" back in those days with a rig like this. I could have "been" Roy, or Paladin for sure.