This old Monte uses choke tubes that are silver in color and the threads were not threaded all the way to the back end of the tube.
The black in color tubes(newer) have the same threads , but do not fully seat as the black tubes have threads that are threaded all the way to the back end of the tube.
I know, sounds a bit confusing.
So I am in search of these silver tubes.
If my memory is correct this change occurred in the early 1990s.
What a great shotgun. It has dropped ducks,geese, quail, pheasants, turkeys, doves and holds its own shooting clays.
Wish I had bought two
I will try to get the Mrs to post a picture, my computer skills are slightly above the Amish, apologies to the Amish.