The G series FLIP-CHIP boards were used in the original PDP-8 introduced in 1965 and peripherals.
They provided special functions and were not sold as general building blocks
like most of the other series.
The G series boards have Green handles.
The following picture links also have descriptions of what is shown in the pictures.
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G083 Disc Preamplifier ( 31K) back of board ( 44K)
G284 Disc Writer ( 23K) back of board ( 32K)
G285 Series Switch ( 29K) back of board ( 42K)
G286 Center Tap Selector ( 32K) back of board ( 43K)
G847E Dual Motor Voltage Control ( 35K) back of board ( 39K)