That's what I thought. Muff.
But, I have played through an old Gibson amp that sounded like that. Years ago. Don't even remember what model.
I’ve no doubt there are amps that can cop that sound. But, his lead sound compared to his rhythm sound suggests either a fuzz pedal, or an entirely different amp.
I can get pretty close to the lead sound with a Stomp Under Foot Violet Menace (Violet Ram’s Head Big Muff clone) and an EQ pedal with a bit of delay and reverb.