IBM Model M type 3193 Keyboard
IBM Model M 3193 keyboard, 1988
This keyboard does not have a Control key.
lots more photos of model M at http://snowdog993.imgur.com/
IBM Model M type 3192-G keyboard, 1985
this keyboard is actually one of the few that you won't see a control key on.
It was made for use with a 3270 terminal connected to a Mainframe where there was no use for a control key.…
The extra keys are related to different shortcut macros that are used in the Mainframe. Meaning, there were 24 different functions to use.
The PA keys are for different Program Access functions. PA1 is the attention key which is like hitting ctrl+C to halt a function. PA2 is used to reshow a screen. So, if you accidentally hit the clear key before you were done viewing something, you can hit PA2 and reshow it.
the PA1-3 keys have different functionality depending on the environment. I have only used PA1 in TSO to send an interrupt.
From what Haiduk has told me, that entire left side was usually made up of custom keys that programmers put there for specific tasks.
PF19 is scroll up and 20 is down.
Here's a list of the default keymaps used in Personal Communicator (another 3270 emulator). http://publib.boulder.ibm.com/infocenter/pcomhelp/v5r9/index.jsp?topic=/com.ibm.pcomm.doc/books/html/emulator_reference11.htm
The key mechanism is buckling spring.
This seems to be used for IBM mainframes.
Affirmative Computer Products manufactures a complete line of keyboards to increase productivity for users moving from iSeries AS/400 Twinax (5250) and zSeries Mainframe Coax (3270) terminals that have 122-key keyboards to PCs or Thin Client / Ethernet Terminals.