IEEE 1275 is the official IEEE designation for the joint Sun Micrososytems/Apple Computer Open Firmware design.
To give an official representation of what it is, here is a brief quote from the Open Firmware Home Page (http://playground.sun.com/1275/):
Open Firmware is the non-proprietary name of firmware complying with IEEE Std 1275-1994. OpenBoot (tm) is Sun Microsystems trademark for the firmware product shipping on over one million SparcStations(tm) and SPARCServers(tm) since 1989. Apple Computer's newest line of PCI bus-based Power Macintosh(tm) desktop systems are shipping with Open Firmware.