Originally Posted By: Daryl Hallquist
Is that a hole in the buttstock or some sort of inlay ?


From the "Hunting_Heritage" article in the link:

"Something you may notice at once is the hole in the buttstock. Yes, it looks a bit unusual but no, it isnt an early version of a thumbhole stock! This is a working gun for harvesting lots of waterfowl and the hole is for mounting, making it easier to fire the big bore from a small boat"

There are several more pics in the article that show the hole more clearly.

A true sign of mental illness is any gun owner who would vote for an Anti-Gunner like Joe Biden.