Up for bid is a set vintage NOS 1/4" 4 track 2 channel head assy, "playback head can play 2 track or 4 track tapes controlled by a latch"(in front of the playback head)  to adjust the playback head's height and could modify for Ampex 350,351,354,AG-350.....as photos(resistance: erase head:3Ω/3Ω,record head:13Ω/13Ω, playback head:375Ω/375Ω) Made in USA  Please see pictures. Thanks for looking and bidding.          Good luck !