U6 and U7 are the CPU EPROMs for a Boonton 4200 pwr meter with opt 01A (GPIB) 
S/N 217. U1 is the GPIB board EPROM

Firmware is listed as V

EPROM data is:

U6	F0Hb	0989	NEC 2716
U7	F1Hb	0989	NEC 2716
U1	F2Hb	0989	NEC 2716


The files are saved in Intel HEX format.