If I remember correctly the ROM on the B&W G3 was actually labelled with printing on the PCB.

On the B&W G3 is looks to be the long SHARP chip at U37 with the pins on only the short ends between "grackle4" chip and the CPU&bus multi jumpers.

On the G4 Gigabit Ethernet and I am assuming Sawtooth as well it looks like it is the same SHARP chip at U7 beside two rows of empty solder pads.

On my G4 Digital Audio it looks like the (again)same SHARP chip at U7 again between the ends of the RAM slots and the slower PATA connector.

Lombard CPU daughtercard has one of these suckers as well under the top RAM slot at U5.

I have not yet looked it up but on all these mobos it is a SHARP LH28F008BVT-BTLI0

Now if you will excuse me I have to put a bunch of computers together/away. :P