I've been floating around the Amiga Facebook group for a while now and recently had a bit of a conversation with a couple of the guys about the different keyboards that were used on the Amiga, specifically on the A500(+).
A little bit of history. When the Amiga first launched it was known as 'Amiga'. Later, this first model was renamed as the Amiga 1000*. This model had a separate keyboard that slid neatly under the case to keep everything tidy. Allegedly, this design 'feature' was one of the reasons for the high cost of production. Another debatable point. The keyboard itself was a compact design, smaller than a standard IBM XT/AT keyboard but it was mechanical i.e. each key had a switch that when pressed sent that character to the computer. According to Deskthority.net, these keyboards were manufactured by Mitsumi. They also had the familiar 'A' Amiga keys, but with the 'A' printed in red.
|A1000 Keyboard - Note Red Amiga Keys|
Pic from Deskthority
Fast forward a year or so. Commodore made a brilliant business decision (one of few) to release a cut down Amiga that would make it available to a much wider audience. This was the Amiga A500 which was the brainchild of Jeff Porter at Commodore. It incorporated the keyboard into the case and a floppy drive in the side in a form factor that was familiar all the way through the late eighties and early nineties. The Amiga, Atari ST and Archimedes all followed this design and it was highly successful.
From the information I have been able to find, the first Amiga A500s were actually released with Revision 3 motherboards. They also included keyboards that closely followed the design of the A1000 in that they used mechanical switches. They were actually Hi-Tek Series 725 and are affectionately known as 'space invader' keyboards. This is because, when a key cap is removed, the shape of the switch closely resembles the space invader characters from the 80's arcade classic.
|Space Invade Keys|
Original image from Deskthority
These early keyboards are easy to spot for a slightly fortunate reason. The plastic keycaps are made of polybutylene terephthalate (PBT) which, according to Deskthority.net is the hardest material used for keycaps. If you know anything about the Amiga you will know the problems with 'yellowing' caused by the bromide used in ABS. This doesn't happen with PBT so these keyboards make themselves obvious by being completely un-yellowed compared to the A500 they sit in. If you find an A500 for sale with an almost perfect white/grey keyboard then the chances are, it's a space invader type. They were only used on Revision 3 and some Revision 5 motherboards (Revision 4 isn't really a thing for the A500).
Another feature of the early A500s is that the case badge is moulded into the case itself rather than being a recessed plastic badge. These are known as 'chicken lips' cases since the Commodore logo looks like a stylised drawing of a chicken. Allegedly. So, the upshot of all this is, if you happen to be perusing a car boot sale in your local muddy field and happen to see a chicken lips A500 with a pearly white keyboard at a decent price it's well worth getting as it will almost certainly be a rare, early model.
While the 'invader' type of keyboard is very nice to use, and is comparable with some of the best mechanical keyboards available even today, they also had a bit of a cost problem. They were not cheap and kept the price of the A500 high. To get around this, new keyboards were developed with a much lower price point and subsequent drop in 'niceness'.
There were two main types of this reduced cost keyboard, Samsung and Mitsumi. Yes, Samsung made keyboards for the A500.
However, the Mitsumi keyboard is by far the most common used on the Amiga A500. It was so successful - if not very good to use for long periods - that the same basic design was used for the A600 and A1200 keyboards as well as some A3000 keyboards. Mitsumi keyboards use 'hybrid switches' which are basically a plastic post that contacts with a membrane that completes a circuit. A spring underneath the keycap provides the 'return' of the key when pressed. The Samsung keyboard was similar but the spring was held inside the keyboard so that the springs are under the posts rather than directly under the keycaps as per the Mitsumi.
|Samsung Keycap, Post and Spring|
a) the worlds smallest screws
b) the worlds slipperiest springs
c) your sanity when you try to put it back together
|Mistumi Keycaps - Note the bigger springs|
Original image from Amigos Retro Gaming
Neither the Samsung or the Mitsumi keyboard offer a particularly good typing experience. The keys travel a little too far, there isn't any real tactile feedback and the general feel is quite spongy and unsatisfying. Both also suffer from the dreaded yellowing mentioned above as all of the keycaps are made of ABS. Despite this, it is relatively easy to determine the make of keyboard an A500 probably has.
Any A500 UK keyboard with a 'small' return key is ALWAYS Mitsumi*. This includes all A500+ and any A500 that has the larger A500 badges rather than the small square Commodore logo. The same basic keycap design is used on the A500, A600 and A1200.
*European keyboards always had a small enter key to allow for additional language characters. I've never seen a Samsung keyboard with a small enter key but they could be out there.
If the return key is the large 'L' shaped key then it could be any of the three available types, so ask yourself the following questions:
Q) Are the keys still very white?
A) Likely to be a 'space invader' keyboard.
Q) Does it have a 'C=' key instead of the usual 'A' Amiga key?
A) Likely a 'space invader'.
If the keys are yellow, take off the top case (if you can).
Q) Does the control board have a single white membrane connector?
A) If 'yes', it's a Mistumi. If 'no' it's a Samsung.
|Samsung - Dual Connector (excuse my dust)|
|Mitsumi - Single White Connector|
The Samsung keyboards use keycaps that are more angular than the Mitsumi. The Mitsumi keys appear softer and more rounded. This may sound a bit vague but if you see the two different types together, the differences become obvious. You might be able to make it out in the two pictures above.
Keyboards. More interesting than you'd think. Possibly.