T -Bone , Porterhouse it all depends on where you and where the butcher was trained , in Europe ,Australia , New Zealand thats a T bone .
A porterhouse , internationally it is called a club steak. In the US and Canada it is also known as New York strip, strip loin, shell steak In Australia and New Zealand it is known as a porterhouse steak or boneless sirloin. from the short loin . Unlike the nearby tenderloin, the "Club" is a sizable muscle, allowing it to be cut into the larger portions.
When still attached to the bone, and with a piece of the tenderloin also included, the strip steak becomes a T-Bone or in the US or Canada a porterhouse the difference being that the Porterhouse has a larger portion of tenderloin included. The "club steak" may be sold with or without the bone. club steaks may be substituted for most recipes calling for T-bone and porterhouse steaks, and sometimes for fillet and rib eye steaks.
Confusing for me when a number for many years the meat cuts I have used and ordered have different names !