Real Greens are linear, FYI. The greens in the Ducky are XM's.
The XM KSB-LE is green and linear – that's the LED model (possibly also the KSB-LK, although the
Xiang Min website has very little details on their switches – I've asked them if they have a table of models and basic characteristics). Ducky order customised 55 cN switches; normal Xiang Min KSB switches are all 60±15 cN.
The tolerance is one factor that bothered Edgar Matias, hence Matias switches having only ±5 cN tolerance for a more consistent feel. Another factor is the metal, shape and thickness of the tactile or click leaf, something Alps Electric paid a lot of attention to, but the clone makers did not.
The most common complaint with "XM" switches (a blanket term given to
T1 to T9 "Mantis" switches) is that they're "balky", that is, they're too highly loaded. The peak force is very high (much more so than the 60 cN rating suggests) and it takes a lot of effort to depress the switch, leading to fatigue and missed keystrokes. Cherry MX clears are also very stiff, but they stiffen at the bottom of the stroke, which you learn to avoid by not bottoming out hard. I couldn't say how the 55 cN custom version compares, and some people like XMs.
I've also asked Xiang Min to clarify this, but according to their website, the factory that originally made their switches opened in 1997, and the original company was founded in 1994. No XM switches can exist before 1997 when the company took the name Xiamen, from the Xiamen factory; they weren't called Xiang Min until 2001.
Any "XM" switches made before 1994 are NOT Xiang Min XM switches. They either copied or bought up an existing design. "XM" just means "the lower shell has four small tabs instead of two long tabs" to most people, as some other clones (e.g. Strong Man) retained the long side tabs. However, the four tabs design goes back before then and is by far the most common lower shell design for clones. The only to be sure with any switch, as you know, is to open it up and examine the internals. For example, I have an old NTC AT/XT switchable board with four-tabs switches that are not XM. No idea what they are. They got called Type IV, but nobody knows who made them. I opened up a switch and found that it doesn't have the characteristic narrow copper "Mantis" click leaf common to most clones, rather, it's a full size classic click leaf like Alps CM and Strong Man.
There's another switch family, the
APC BSW family, that appears to be both current and unrelated to Xiang Min, as Xiang Min switches all have "KSB" part numbers, not "BSW". APC switches appear to very closely resemble Simplified Alps Type III, tentatively suggested to be Strong Man switches (Strong Man went out of business a few years ago, not long after Chloe was enquiring about getting samples from them). Compare
Sandy's Type III photos to the kbtalking page (search for "APC") although modern APC switches are blue like the Type III.
There are a *LOT* of Z mount switches out there. Fuhua ("Fukka") switches (discontinued as of early this year), Xiang Min KSB and a number of others are all pin-compatible with Alps CM, i.e. you can harvest switches from a vintage blue Alps CM board and put them into a Dell AT10* (Alps CM complicated), Ducky 108* (custom XM), Filco Zero (Fukka/XM), Matias Tactile Pro (Alps CM simplified/Strong Man/Fukka/Matias Alps), Matias Quiet Pro (Matias Alps), some SIIG MiniTouch boards (the XM ones), or any other desirable board.
There are also Z mount switches that are not Alps pin compatible, e.g. Monterey, "Aruz"/"Hash". These will provide a supply of vintage keycaps, but you can't swap the switches out.
Basically only the insane continue to care about Z mount switches as it's a nightmare to figure out who made what and when. It wasn't until I asked Edgar Matias the other week, that anyone even appeared to know what "XM" meant, only that it was a name bandied about with no meaning behind it. XM is Xiang Min Co. Ltd., Chinese: 祥敏企業有限公司 – Xiang Min Enterprise Co. Ltd. It might be years before we figure out APC, and I can't ask Strong Man anything as they no longer exist. Fuhua (Foward Electronics) we know bought out Alps Taiwan, which is why their switches are basically Alps Electric's own simplified design. I don't know whether their characteristic ping, due to an overly thin click leaf, was a mistake made by Alps themselves, or a cost-cutting measure at Fuhua afterwards. You'd have to play with an original, pre-Fuhua Tactile Pro and compare: the very first ones used the last million Alps Electric-made Alps switches ever produced.
[TL;DR – Give up and go home. Alps are not for you. Trust me.