You are bidding on a pair of NIB Mullard "longplate" ECC83 / 12AX7 with square getter and double getter support from 1956! They have the following date codes: mC1 B6F and mC1 B6I. Made in Blackburn. The tubes test like new on Neuberger 370. Sold as is.Be sure to take a look at my other auctions for more rare ECC83 as well.