ECC83=12AX7 Mullard UK BVA long plates "O" getter like new 1958 (f91 series) (1.2/1.2ma)1 low noise tube) ECC83=12AX7 Mullard UK BVA long plates "O" getter like new (f91 B8E=1958) in white box good "upside down" printing 1 section) 1. 2ma Gm=1500 1 section) 1. 2ma Gm=1500 (f91 B8E=1958) (f91 series, 2nd series) 17mm = long plates "O" getter halo copper grid posts big midrange, sweet high end, very rare