This unused, old stock 12AX7A was made by Shuguang in the now closed Beijing factory before they moved to Changsha. They are the highly sought after version that are no longer made and getting difficult to find. It is a high quality preamp tube and is regarded for its clarity and brightness. These tubes are OEM intended for installation in new production amplifiers and have no brand name on the glass. They are stock tubes in many amps including Marshall and Mesa Boogie. Considered by many to be the best sounding preamp tube available.
Here is what one of my customers wrote about them:
“NOS Shuguang Foil 12AX7 preamp tubes! Excellent Quality! Woke Up My JCM 800! A+!”