(!) (#1 6688 Single) 6688=E180F Rogers Holland NOS "D" getter gold pins 1958 (18ma)
(!) (#2 6688 Single) 6688=E180F Amperex PQ Holland NOS "O" getter gold pins 1962 (12ma)
(!) (#2 BEST 6688) 6688=E180F Amperex PQ USA NOS/80% gold pins "D" getter halo 1959 (9.2ma)
(!) (#3 BEST 6688) 6688=E180F Amperex PQ USA NOS/80% triple mica gold pins 1962 (9.2ma)
6688 GE 5 Star used/good (7.2ma)
6688 GE NOS 1966 (9ma)
6688=E180F National UK black plate NOS unknown maker (14.2ma)
6688A=E180F Mullard branded RCA gold pins NOS 1973 (17.5ma)
JAN-6688=E180F Amperex NOS gold pins 1976 (13.8ma)
JAN-6688=E180F Mullard branded Philips Holland gold pins 1966 (12.5ma)
