GRASS Instruments Polygraph Low Level DC Pre-Amplifier 7P1G UNTESTED

Grass Instruments Polygraph DC Driver Amplifier 7DAL UNTESTED

GRASS Instruments Polygraph Low Level DC Pre-Amplifier 7P1D UNTESTED

Grass Instruments Polygraph DC Driver Amplifier P511 A.C./ Pre-Amplifier Part S2

VINTAGE Grass Instruments LM4 Lesion Maker / electronics Sci Fi Prop Mid Century

GRASS Instruments Polygraph Low Level DC Pre-Amplifier 7P1J UNTESTED

GRASS Instruments Polygraph Low Level DC Pre-Amplifier 7P1F UNTESTED

Vintage Grass Instruments Lab Equipment: Polygraph 1DAG DC Amplifier & 7P1G Pre-