It is a good amplifier pentode. Quite similar to the 6SJ7 in terms of electrical properties. As to sonics, probably quite circuit dependant, no?Alternate designations are the 6267 and Z729
Often used as the first stage in the Mullard amp. EF86>>{twin triode LTP}>>PP finals. Direct coupled usually so as to use an acceptable tail resistor in the phase splitter. The Eico HF50 went EF86>6SN7>EL34 to a nice Chicago OPTx.
cheers,
Douglas