IBM Model M grey barrel plate?

snuci · 30 Jun 2016, 18:20

I am cleaning a bunch of IBM Model M's and noticed one peculiarity. My early industrial Model M with the square black logo on the right (which is missing at the moment but I'm working on that) with part number 1390653 has a grey barrel plate. I can't recall if I ever seen this before or if it's unique to a certain set of Industrial M's. My other Industrial M's have either black or white barrel plates as the normal Model M's but I'm just wondering how common this is? Additionally, is there any other factory colours of barrel plates that were manufactured by IBM? Just curious.

I must say, this keyboard looks pretty cool without any key caps on. The second pic hopefully shows the dark grey colour better.

: IBM 1390653 - grey barrel plate; IBM 1390653 - grey barrel plate.jpg (350.35 KiB) Viewed 2183 times

: IBM 1390653 - close-up; IBM 1390653 - close-up.jpg (282.46 KiB) Viewed 2183 times

emdude · 30 Jun 2016, 18:32

I don't have pics right now, but I also had an '88? Model M with a gray barrel plate like the one on your industrial. Just going from experience (work on at least a dozen Model Ms from various years), but I believe all of the early Model Ms up to '87 had black barrel plates, then from '89 until Lexmark introduced drainage channels, Model Ms had white barrel plates.

As far as I know barrel plates with drainage channels were all black. I don't know much about late Lexmark-era Model Ms though.

So I think IBM only briefly made barrel plates in dark gray, around 1988. Do you have a manufacturing date on that Model M?

Chyros · 30 Jun 2016, 19:26

I have several with black barrel plates that are kind of marbled with shiny grey, as if there was graphite on them. Is it anything like that? I find it hard to judge the colour from the pictures.

clickykeyboards · 30 Jun 2016, 21:15

Another interesting tidbit about the grey/dark brown barrel plate is that the plastic composition of the barrel plate is slightly different than other barrel plates. Having personally drilled and screw-modded thousands of model M keyboards, the black barrel plate and the white barrel plates have no problems with drilling and the drilled residue comes out as cut swirls.

For some reason, in the case of the grey/dark brown cases, the melting point of the plastic is lower and when using a high-speed dremel, the speed of the drill bit can melt the plastic onto the drill bit. This then requires the drill bit to be cleaned after drilling each hole and scraping off the melted plastic. My guess is that this was related to the melted rivets technique used to close the inner keyboard layer assemblies.

What year is 1390653 in the original post?

XMIT · 30 Jun 2016, 22:24

clickykeyboards wrote: ...the plastic composition of the barrel plate is slightly different than other barrel plates...

I'd like to have a list on the Wiki somewhere of all the plastics used in various generations of the Model M: ABS space bars on the Greenock M, PBT key caps, PVC cases? I don't know what plastics are in use for the barrel plate.

snuci · 01 Jul 2016, 00:29

Chyros wrote: I have several with black barrel plates that are kind of marbled with shiny grey, as if there was graphite on them. Is it anything like that? I find it hard to judge the colour from the pictures.

Here's a better pic in direct sunlight. I put a black plastic plate next to it for contrast. I think I have seen one like you describe where it looks like there is swirl marks in it like they mixed it and didn't finish but threw it in the molds anyway. Does that sound possible? This one is definitely grey and noticeable or I would have just breezed past it. This one is a solid colour.

: IBM 1390653 - grey colour; IBM 1390653 - grey colour.JPG (240.29 KiB) Viewed 2090 times

This one is March 7, 1988. Seems kind of late but also notice the ID number. The 5394th one made?

: IBM 1390653 - rear label; IBM 1390653 - rear label.JPG (299.47 KiB) Viewed 2090 times

fohat · 01 Jul 2016, 00:46

Every one that I have drilled (probably at least a dozen, 2/3 black + 1/3 pearl) has produced curli-cues of plastic using a Dremel at low speed and trimmed up easily with a sharp Xacto afterwards.

I have never drilled at high speeds, in fact I always bemoan the fact that my Dremel does not have an even lower speed.

Chyros · 01 Jul 2016, 01:14

snuci wrote: Here's a better pic in direct sunlight. I put a black plastic plate next to it for contrast. I think I have seen one like you describe where it looks like there is swirl marks in it like they mixed it and didn't finish but threw it in the molds anyway. Does that sound possible? This one is definitely grey and noticeable or I would have just breezed past it. This one is a solid colour.

Yes, that's definitely much greyer than I thought. And indeed, the swirly thing, almost like frost crystals on a pane of glass, is what I was describing. Quite a lot of Ms I've found have that effect.

rootwyrm · 01 Jul 2016, 20:22

That's definitely grey. Been a while since I've seen one of those. They're pretty uncommon to put it mildly, but they do exist and they're the real deal. I don't know what plastic they are either. They seem to be specifically associated with industrial applications, so my guess is that it's a higher melting point plastic or it's more resistant to harsh chemicals.