What to look out for when buying Model Fs and Model Ms?

There are things you may want to keep in mind whilst looking for and purchasing a Model F or Model M keyboard. A lot of these keyboards may be very old and subject to age-related issues that you want to know about beforehand as resolving them could be time-consuming. There might also be nuances and customisations you want to be aware of, as sellers may not disclose, either an oversight or on purpose. Assembled with help of the /r/ModelM Discord server for suggestions, this part of the ASK Buyer's Guide will cover some of these and help you spot and possibly overcome issues.

Contents

Possibility of rubber dome Model Ms

Contrary to popular belief, a significant minority of the Model M family doesn't use buckling springs. Starting as early as 1993, IBM introduced a version of the IBM Enhanced Keyboard called the Basic Keyboard where the buckling spring actuators are replaced with rubber domes. IBM's marketing term for these is Quiet Touch, which was their umbrella term for alternative key-switch technologies that weren't designed to be audible. IBM-branded Quiet Touch Model Ms can usually be identified by their part number - 7xxxxxx usually indicates the keyboard is rubber dome. However, Lexmark made and Unicomp continues to make Quiet Touch branded keyboards with differing part numbers. You can check the part number against the Keyboard Part Number Database to find out what switches a given known IBM/Lexmark/Unicomp keyboard should have if you want to be sure. If the part number is not in the database or want a second opinion, you can inquire on /r/ModelM Subreddit for advice or ask the seller to remove a keycap and see if the actuators or keycap stem look like what's shown above.

Possibility of broken rivets on Model Ms

Most Model Ms (notably excluding Models M1, M2 and M15) have discrete internal assemblies that are held together at tension via many melted plastic rivets. Those rivets are known to break. Losing a handful of rivets that are not adjacent to each other is generally not fatal, but losing many that are clustered in one area of the keyboard will lead to a loss of tension that can at first lead to mushy-feeling keypresses and then will stop registering as it gets worse.

If you're worried about rivet loss and you don't have the means to fix the issue yourself (see below for more details if you do), you could possibly ask a possible seller to check if they can hear any rattle inside the keyboard. Unfortunately, this isn't a guaranteed test since rivets towards the front of the keyboard may still be held partially in place thanks to the bottom case piece pressing against the internal assembly, or any broken rivets could have escaped through the speaker grille most 101/102-key Model Ms from 1985 to 1995 have. The most obvious request you could make is to ask the seller to open the keyboard and take a photo, but most buckling spring Model Ms use 7/32" (5.5mm) flanged hex-head screws and sellers may not have the right tool on hand, so this isn't usually a viable option. If you're buying a Model M in person or have the opportunity to pick up a keyboard you're buying from the seller, you could see for yourself if any keys feel mushy (although rivet loss may not be the only cause of such feeling).

If you decide to buy the keyboard anyway and/or find the keyboard is missing rivets on arrival, all is not lost. Practises known as screw or bolt modding can be used to replace the lost rivets with screws or bolts (respectively) to regain tension on the assembly. This can be done yourself (guides on how to do this like Bitten's Model M Restoration Megaguide exist) or can be professionally done by experienced 'bolt modders' such as long-time practitioner Brandon @ clickykeyboards.com.

Potential issues with pre-bolt/screw-modded Model Ms

Considering the issue explained above, buying a Model M that's already bolt or screw-modded may be an attractive option if you don't have the confidence or resources to do it yourself. However, keep in mind that it's possible to do a bad job with such modding, potentially causing longevity issues with either poor workmanship, by using improper fasteners or using non self-tapping screws instead of self-tapping screws^[2][2]
BittenEite - Bitten's Model M Restoration Megaguide [accessed 2023-01-09]. License/note: any photos used with written permission., etc. Thus it's recommended to only buy pre-modded Model Ms that have clear photos of the work done and all work is disclosed, and the right fasteners used match the type of job completed (for example, using bolts on a screw mod or vise versa). This is said mainly because there's a risk of cracking the barrel plate when such mods are performed. A cracked barrel plate can be [somewhat] repaired or replaced with a new one from Unicomp, but it's a potential issue if left unchecked. If there are no photos available showing how the work done affects the keyboard from the barrel plate's point of view, I'd recommend at least asking questions or just looking elsewhere.

Spotting lookalike "Model Ms"

The Key Tronic E0360X family are keyboards that bear a strong overall resemblance to the IBM Model M Enhanced Keyboard and can be misidentified as such, especially in poor quality photos and videos. As they only used rubber dome key-switches, a prospective Model M buyer may want to ensure there is no confusion. Despite the resemblance, they're not supposed to be fake Model Ms - they were legitimate products and Key Tronic even used the platform for the original Das Keyboard. There are some telling differences.

The are other Model M lookalikes that haven't been documented yet - in my opinion, these Key Tronic keyboards happen to be the most prominent of such keyboards. If you have reason to doubt a different keyboard that looks like a Model M as being one, I would recommend using the above as methodology for analysing specific details.

Spotting fake "Model Ms"

On the Chinese online shopping platform Taobao and its second-hand market Xianyu, 'clone' Model Ms with Alps switches have been spotted on multiple occasions. Their existence has never been confirmed in IBM documentation, they reuse known buckling spring Model M part numbers (IBM would normally assign new part numbers or RPQ numbers for such changed keyboards), and have blatant visual issues that IBM would unlikely allow past their quality control process. The easiest way to spot them is through their branding, flip-out feet and the lock-light overlay.

Spotting fake industrial Model Ms

For several years, Unicomp sold Lexmark-era industrial grey Model M cases to consumers who could use them to create their own industrial-style Model Ms, a practise popular due to the high price of real from-factory industrial Model Ms. As such, these cases can be used by resellers to repackage an ordinary Model M and sell it for a higher price. To be clear, most of the parts involved themselves are not fake IBM/Lexmark/Unicomp parts but they can be assembled into a kitbash that wasn't what it's supposed to be. If all you care about is getting a more affordable industrial-style Model M regardless of whether it's genuine you can skip the rest of this section. If you care about getting a real industrial grey Model M, there are a few things you can try spotting:

Detached spacebar stabilisers on Model Fs

Some Model Fs such as the F/XT, 3104/3178 and F/AT are known for having an integrated spacebar stabiliser that resides underneath the barrelplate. Whilst this technically protects the stabiliser from some things, it also makes it vulnerable to being detached when someone [carelessly] tries removing the spacebar and makes it near impossible to reattach without complete disassembly of the keyboard. As such, it's generally advised to never remove a Model F spacebar unless you know what is required to reattach/repair it. Without the stabiliser attached, the spacebar will be floppy, bind on off-centre presses and maybe rest lopsided. Given the latter issue, it's possible to spot problematic spacebars yourself in a listing's photo. It may be worth asking the seller to confirm the spacebar is stabilised correctly (ie, can be pressed anywhere on the bar and it moves smoothly). It's possible to fix the spacebar yourself via a complete dissembly or using performing a string mod but they can be delicate to do.

Possibility of degraded foam on Model Fs

All Model Fs have a foam layer in the middle of their assembly that helps with ping dampening and holding the individual barrels in place. Model Fs (especially early ones) can suffer from foam degradation that may compromise the firmness of the barrels, leading to wobbly keys. This issue isn't as common as Model M rivet breaking and the issue is not usually fatal for the keyboard but can be an annoyance.

If wobbly keys are a potential issue for you, you could try asking the seller to check for excessive key wobble - if there's any present, degraded foam is the likely culprit. Keep in mind that the keyboard may otherwise still work and it's possible to replace the foam yourself. Model F assemblies are easier to open non-destructively than Model M assemblies, usually requiring you to twist several tabs to remove the backplate. 2mm neoprene rubber is a common go-to as foam replacement, which you can buy yourself and manually punch the required holes for each barrel or buy pre-punched. On reassembly, it is recommended to use several small spring clamps or C-clamps around the edges to help hold the assembly together and a large fixed-end clamp like a pipe clamp to align the barrel and backplates whilst you fasten the tabs to secure the entire assembly together. Avoid cheap plastic clamps if possible since they may break under pressure.

Possibility of cracking [General]

Cracking is a potential issue with most aged plastics that you want to be aware of. This presents an issue for especially the heavier keyboards such as 104-key "unsaver" Model Fs, 122-key Model Fs and Type I and II 122-key Model Ms, which have been observed to have small cracks on their top case piece on many occasions, possibly due to the stress of being moved around with their heavy inner assembly in tow. I would recommend you check available photos of listed keyboards for these cracks and they present a possible liability [to get worse] in shipping. If you still want to purchase the keyboard, it might be worth asking the seller to get additional assurances that the keyboard will be packed well for transit.

Sources

ASK. Admiral Shark's Keyboards original content. License/note: CC BY-NC-SA 4.0.