Hey everyone I poked around in an old 50's-era reel-to-reel tape recorder and found some tubes. One was a 12AX7 that I'm assuming is a Mullard. The code is MC1 B6H. I've included a pic of the tube, too. I'm out of town and can't try it in my amp, so I'm not sure how worn it is or if it's microphonic. Any thoughts on this tube? I'll check out the other tubes in the recorder, too. Thanks!