"from the looks of it someone may already hit that receiver with a torch. You can see the discoloration from heat. If they did, the temper may be in question."
"sold for $130 on gunbroker."
FWIW. Over here, that receiver is just scrap in the eyes of the law. Machining or welding the receiver invalidates proof. The proof houses would refuse to accept it for testing. It can never legally be used again in a shootable gun. It matters not whether it is the last receiver of its type in the world, rarity is not an excuse. Scrap is scrap.
In the eyes of an undiscerning collector it might be collectable scrap - but it is still scrap.
"Or was this just opportunity knocking?"
No, just a way for someone to waste $130.