Symbolics earlier style keyboard (PN 364000)
This keyboard is interchangeable with the later versions (PN 365407), it just looks less "metallic". It has the advantage of a cable which unplugs at both ends, which makes it easier to carry about and stack away. It is a bit thicker too, measuring 6.4cm (2 1/2 in) max thickness and 23.5cm (9 1/4 in) by 47cm (18 1/2 in). The key caps are identical. The last version (rev C) of the 365407 keyboard had LEDs in the Caps Lock and Mode Lock keys, earlier revs did not; I was told that Rev C keyboards were required for MacIvory via ADB box, but I have found no difference (they all seem to work).
Under key caps.
(see also new-style keyboard key-caps internals)