classics I threw away or sold ... foolishly

Fred Cisin cisin at
Wed May 18 18:17:32 CDT 2016

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.

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