Apple System Profiler reports the revision as $77D.45F1

The Rev "B" ZIF ROM was installed in the Power Macintosh G3/266(late), 300 and 333 models, all styles(Desktop, Minitower and the All In One machine). Some of the 300 and 333 models have Rev "C" ROM chips installed, their fuctionality is basically identical.

Rev "B" ROM front side of chip

Rev "B" ROM rear side of chip

These are the markings from the frontmost side of the Rev "B" ROM chip. Note that the part number between the chips has changed to 600-6589.

Rev "B" ROM Rear Leftmost side of chip

Rev "B" ROM rear rightmost side of chip. Note the designation has changed from -01 to -02