I have a keyboard that looks exactly like that [marked only 556-712-01 and A110H004451 ] but without the colour key legends; it's a cost-reduced 'board for the RT PCs, either type 6150 or 6151. The RT was IBM's first RISC machine and is the predecessor to the RS/6000 / iSeries / whatever it was last known as.
Some (earlier?) 'boards for the RT were basically US 101 Enhanced buckling spring things [P/N 1392366 ], resembling the more familiar P/N 1390131, but the right "Control" key is marked Action, and the number pad keys don't have the "num lock off" navigation legends. Also, the cable (I don't know if it's fixed or not) has that 6-pin AMP MODU connector.
Here's the only pic I have of mine (Laurie's lighting trick isn't available right now):
The keys on these have a nice travel distance, but seem to almost entirely bottom out on actuation (I can't actually tell, since I don't have a RT...). It's funny that the PCjr is mentioned, since the keyswitch technique looks very similar to that used in the PCjr's later keyboard; see
zoOoz... the domes however are IIRC chopped up a bit, and are all black. This shot of the keys from the inside looks very familiar:
In general, none of the typical IBM over-engineering is present; eight Philips screws hold the back on, and there are a multitude of screws holding the innards to it. The PCB is simplistic, and the only IC is a mask ROM... no trace of any P/Ns, FRUs or house numbers anywhere.
Anyway...
announcement letter time.
Letter #
186-011 - IBM 5085 GRAPHICS PROCESSOR MODEL 1A - MORE STANDARD FEATURES AND FUNCTION FOR THE IBM 5080 GRAPHICS SYSTEM:
o Functionally enhanced to be capable of attaching to an IBM RT
Personal Computer which includes the capability to switch the
keyboard and 5083 Tablet between the 5085 and the standalone RT
Personal Computer processor. The new Graphics keyboard has a
built-in numeric keypad (with plus, minus, multiply, and divide
operations for ease of use) and a thin flexible cable for easier
placement and movement....
FUNCTIONAL ENHANCEMENTS
New functions in the 5085 model 1A are:
o A Graphics Keyboard (#4651) (graphics, 3270, personal computer
functions keyboard). Includes a numeric keypad and 16 dual
function keys (providing 32 possible program functions). When
the 5085 model 1A is connected to the RT Personal Computer, the
keyboard and the 5083 Tablet can be switched between either the
5085 or the RT Personal Computer....
GRAPHICS KEYBOARD (#4651): A low-profile, flexible cable attached
keyboard which can be adjusted easily to either of two surface
inclinations to match the user's preferred hand position. Has 101
keys which may be operated with or without audible feedback. The
keyboard is arranged in four clusters of keys. Three of them are side
by side (left to right) with the fourth located at the left rear.
The clusters are:
o 58 keys including special standard keys for engineering graphics.
This keyboard supports Caps Lock. Caps Lock applies only
to the alphabetic keys in this cluster and Shift Lock applies to
all keys in this cluster, but only in this cluster rather than
the total keyboard.
o 10 keys for cursor control, and special functions, such as cancel
and switch keyboard.
o 17 keys in a keypad arrangement for easy entry of numerics.
o 16 Program Function (PF) Keys arranged in a horizontal row at the
top of the keyboard.
In 5080 graphics mode where lighted tops are not required,
use of upper and lower case shift in conjunction with these 16 PF
keys allows the PF keys to emulate all 32 keys of the Lighted
Program Function Keyboard (#4710). However, nomenclature on this
keyboard (#4651) does not map identically to the nomenclature
used on the Alphameric (#4631) and the APL (#4641) keyboards. For
example PF2 on the new keyboard corresponds to PF3 on the
Alphameric and APL Keyboards. Normal PF key function is
supported in 3270 mode.
Three indicators on the keyboard provide the following status:
o Keyboard association status (association with the 5085 or RT
Personal Computer)
o Numeric Lock status
o Caps/Shift Lock status (see note under first key cluster
description)
The cable required to attach the keyboard to the 5085 is
flexible and permanently attached to the keyboard.
Note: #4651 is the only keyboard available for the 5081 model
1A.How about that?
Of course, this makes me wonder about the
original model of the 5085 (letter #183-145) going back to '83:
Peripheral Device Features
Alphameric Keyboard: This feature is a low-profile, cable
attached, EBCDIC typewriter-like keyboard which can be adjusted
easily to any of three surface inclinations matching a user's
preferred hand position.
The keyboard has 104 keys that may be operated with or
without audible feedback. The key arrangement has four clusters
of keys:
. 10 special function keys.
. 59 keys in QWERTY arrangement, plus special standard keys for
engineering graphics.
. 11 keys for cursor control and the functions of shifting
between 5080 graphic and 3270 modes.
. 24 program function keys arranged in two horizontal rows of
twelve at the top center. (In 5080 graphics mode, these PF
keys can be used in place of the first 24 lighted program
function keys if lighted tops aren't required. Normal PF key
function is supported in 3270 mode.)Does this layout sound familiar? 
