2 old stock matched hard vacuum seam-top 12bh7a matsu/mullard preamp audio tubes w/ limited-run rare gold posts!
the british supplied expertise and tooling via 'transfer of technology' resulted in several critical audiophile advantages:
same anodes, micas, electrode geometry, glass envelope, spot welding, grid wire spacing and cathode processing chemistry!
revered for their warm sound reproduction, these direct japan imports are carefully curated top echelon vintage 
these 'secret' audiophile tubes are popular 12au7 ecc82 plug-in alternates and even include oe fragile national boxes
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full amplification test pristine match 110/108 ~ 108/109 % mutual gm (65 % good) + useful life test pass! (important)
our unique mutual gm output test applies 225 vdc simulating actual circuits plus filtered dc + leak short gas check
we pride ourselves on a proprietary value-added complete refurb screening and deox process, and free postage!
give 100+ session hours w/ your specific amps voltage to fully cure (breakin is important)
ships well packed worldwide ~ authentic vintage hifi audio curation by caliacoustics