6V6GT "Summer-Of-69 Special" TAD Premium Matched tubes pair with metal base. The 6V6GT "Summer-Of-69 Special" is a 6V6GT version from 1969 (also in 1967 and 1968) made exclusively for military purposes in China. These are already characterized by a significantly better manufacturing quality compared to the commercial comparison products. These tubes pass through TAD QC processes, are carefully crafted with tightest static (Iao) and dynamic (Gm) tolerances into pairs and quartets and receive both TAD test label, TAD brand and the TAD warranty. Unfortunately, these are only available in limited quantities.