This device is used for field testing and alignment of IBM 3420 tape drives. (such as X1640.99 L) "Tom Parker" is written in black on top of unit.. "Tom Parker" is scratched into left side of unit.. On back of unit there are 2 white stickers, the first says "Tom" the second says "Parker" in marker, under marker is written "3420 tape test" and "1265342"
