Looks like fairly standard 3 x 6 subway tile.

Measure the tile.

IMO that is polished marble since the grout line is almost nonexistent.

https://www.amazon.com/Spanish-Marfil-Marble-Polished-Subway/dp/B07VJCJ764

My guess is they used 2x4.

The offset can also make a difference and for a more vintage look suggest off 1/3 or 1/4.

Here's the source of the photo. It sounds like that tile might be pretty old. That doesn't help to answer your question though. :) It's so pretty! Below is a closeup of the tile before it was repaired. Hard to tell what kind of tile it is; maybe off-white porcelain? This might be a nice option for you: https://oasistile.com/products/delicate-white-3-x-6-matte-porcelain-tile