An Ampex 351 microphone preamplifier with a white and black label reading: [4]. The preamp features a small meter at center behind a glass front along with various black dials and metal switches. An Ampex manufacturer’s tag on the back reads: [AMPEX / CAT. NO. 02-30960-11 / SCHEM. 84-0070 / CONT. NO. 29723 / PROTECTED BY U. S. AND FOREIGN PATENTS].