Spencer Rifle 50077

[macinyart]

This rifle bought at auction some time ago in Northeastern WI is interesting in that the barrel is 36' long (almost certainly re barreled from OEM) and has no corresponding number under the foregrip. The number stamped on the rear of the breech is 50077, there is an uppercase "M" stamped on the left side of the breech (inspectors mark?). I cannot find the history of this rifle likely due to my inexperience in the gun field.
If anyone has the urge to give me a hand with this, I would be grateful. You don't have to do the work, but pointing me in the right direction would be appreciated. Thank you.

 

[hrobalabama]

I think there are some posters here that have access to Springfield Research Center. If you will provide the serial#.
Is this a rifle or a re barreled carbine? Photos will help. Is it CW or Indian War? Does it have a Stabler cut off? Take digital photos and upload them to your post.

 

[Youngblood]

Not sure on number range but the unicorn of Spencers is the ultra rare Sporting Rifle. Kinda like a Sharps buffalo.