I'm fairly certain the case was purchased with the rifle. No documentation to prove it though. the rifle serial #63XX puts it in 1938, and the barrel jacket code & butt plate #s match.

No serial # on the barrel jacket I have found yet. I've only seen one other case for sale separately, and 2 for sale with rifles. All were JMB Model 8-81s. Care to guess auction values?
To answer some questions:
==> While dickering nothing was said about the case, SURPrize
==> Yes, the mask was a cross between IronMan & Zorro.
==> The brass cleaning rod is definitely a period piece,
never have seen one like it.
==> Incidentally, I found the correct grip cap for the rifle as well, It has a new home.
Is there any interest in these cases? I've relatives that restore Wurlitzers, Rockolas, & Seeburgs. They have resources for leather goods, plating, and high quality reproduction cast parts. No idea about cost for now.