(!!!!) (Best Pair #2) 6688=E180F RCA by Mullard UK gold pins 1974 (8.8ma and 9.0ma) (strong Gm)
(!!!) (Best Mullard Pair) 6688=6688A=E180F Mullard Philips SQ and Mullard RCA gold pins NOS 1971-1974 (11.5ma and 11.5ma)
