Master Cylinder - 67 Barracuda converted to front disc brakes
That looks like a drum drum master.
Masters come in 3 sizes (basically) for our cars
1 inch is the typical standard size for our cars. (power or manual, disk or drum)
15/16 will decrease the amount of leg force but increase the travel
1-1/32 will increase the leg force but decrease the travel
Disk drum
Drum drum