This coating gives them the appearance of being used but make no mistake, it is normal and they are GREAT TUBES.These are thought to be the best of the 6BQ5/EL84 produced in the USA. The GE 6L6GC power tubes in this premium matched octet have gray plates, dual side getters, black bases, and the 188-5 factory code (Owensboro, Ky).The late 1970s Sylvania 6550 power tubes in this precisely matched quad have welded gray plates, 3 getters, and metal collar bases.The yellow print on the glass has the Philips logo and "6V6GTY U. Both tubes test as new and are matched for both current draw (m A) and Gm.
date code 1960 - date in white writing is (1 14) 1961.
In Fender amps they will win every single time over the mass of 12ax7 tubes out there.
The late 1970s GE 6550A power tubes in this precision matched pair have crimped gray plates, 3 getters, metal collar bases, and 188-5 factory code (Owensboro, Ky). Tubes test as new and are precisely matched for both current draw (m A) and transconductance (Gm).
ECC88/6DJ8 code: GA4 (NOKEY)0L2 NOKEY manufactured in Heerlen, Netherlands. Note that in 1961 the globe logo is used on the box.
8 in code means 1958 - (6009) 9th week of 1960 is the date in white marking. In transitional years they may have used up the old boxes while simultaneously using boxes with the new globe logo.