There was a York Monster sousa sitting in the instrument storage room at the first college I attended. It was in bright silverplate and identical to the York sousa pics in this thread. Unfortunately, it was not in good playable condition because it was missing bits, and the gooseneck section was messed up and was leaky. I still tooted some notes on it and it still had a beautiful sound despite the issues. I can only imagine how good that sousa would play if it were properly fixed and had bitslost wrote:Pretty sure the bell collar for the 20k/38k is 7.25 but someone please correct me if I'm wrong since I'm relying on previous posts from these boards.
So I'm gonna still contend the York Monster 5/4 Sousaphone is larger than Conn 20k & 38k 5/4 size sousaphones in terms of bore size, bell collar size, overall height, and attitude (Shields myself from the tomatoes thrown by 20k owners).

That college also had a couple old satin-silver Conn 20K sousas, and at least 3 satin-silver King 4/4 sousas. We played the King sousas.
That said, I'd put the York Monster sousa in the same 5/4-ish size category as the Conn 20K, King Giant (I played a King Giant in H.S.), and Yamaha YSH-411.