On Wed, 18 May 2016, Jarratt RMA wrote:
1. HP 150 and 9121D, [...]
I have one of these. It it a pretty ordinary 3.5" floppy as I recall. Really
pleased with my example! It is just missing the printer in the top of the
monitor.
There have been a few minor changes in the disks, mostly the shutters,
over the years.
1) The first one that I saw did not have a shutter. I don't know whether
that was intended, or merely a shortcut to try to get the first
engineering samples out the door.
2) The next ones had a manual shutter. Manually slide it to open,
manually slide it to close.
3) The first ones that I saw on an HP150 I think may have been "pinch"
disks. If you slid the shutter open, it latched. Or, if you banged the
disk on the table (which couldn't have been good for the life of the
shutter latch) Some computers opened it automatically. When you took the
disk out, the shutter was still open. There was a spot on the corner of
the disk to "pinch" that released the shutter, and it closed. Some were
labelled, "PINCH", some just had an arrow pointing to the pinch spot.
4) When automatic shutters (as used now) appeared, many of the disks still
had the arrow pointing to the pinch spot. 'Course now that was "to show
you which side of the disk goes into the drive".
Some of the early disks had a breakout tab for write-protect, before they
went to the slider.
