[Rod B]

Define barrel extention. Is this a Cutts compensator or possibly a poly choke?

Rod.

 

[Rod B]

Looked up the schematic in "The Gun Digest Book of Exploded Firearms Drawings".
Yes you are right it is part of a larger tubular assembly;however there is also the smaller hooked piece & a rivet listed.
I found the schematic somewhat small & not totally clear in its description of this classic shotgun.

Rod.