Monogram SMK derivative series

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Monogram SMK derivative series
USw LXBB01 -- recognition.jpg
Switch type Linear, alternate action
Sense method Metal leaf
Keycap mount SMK cruciform (unconfirmed)
Cherry MX mount (unconfirmed)
Switch mount Plate mount

Monogram SMK derivative series refers to a series of SMK J-M0404 series clones and derivatives, distinguishable by the use of an unclear but readily identifiable monogram. There is a suggestion that these switches were manufactured in Hong Kong.[1]


Base branding is an unclear monogram

The base of each switch is branded with a monogram that appears to depict the letters 'C', 'S', 'C' and 'O', possibly in this order (reading outside to inside and top to bottom). These switches have never been found in any branded keyboard, so the identity of the manufacturer remains a mystery. Even the orientation of the monogram is not known for certain.


This series is a fairly close copy of SMK J-M0404 series. The types examined so far have two raised contact ridges along the crossbar of the stationary contact, just as with SMK switches; HTK switches only have one central raised area. The rear of the movable contact is copper colour in photos, suggesting that the whole contact is made of phosphor bronze; the front appears to be plated.


The series contains a number of different switch designs. Some have a keycap mount that appears to be SMK compatible, while others have a keycap mount that appears to be Cherry compatible. wrote, "是台灣參考NEC軸而改良的嗎? 為了配合Cherry MX的鍵帽 ?",[1] the implication being that they are Cherry MX mount, which appears to be the case from photos of the switches in question (USw LXBB01 and LXRB01). Some switches with USw LX designations are likely to need reclassifying with USw LM designations once the keycap mount is confirmed.

All known switches are linear. The similar HTK switch has been found with click leaves, but this has not been observed in this series.

Known examples include:

Designation Keycap mount Type
USw LXBW03 -- variants table.jpg USw LXBW03 SMK? Alternate action illuminable
USw LXBW04 -- variants table.jpg USw LXBW04 SMK? (angled) Alternate action illuminable
USw LXBB01 -- recognition.jpg USw LXBB01 Cherry MX? Momentary
USw LXRB01 -- recognition.jpg USw LXRB01 Cherry MX? Momentary, heavier weight?

Alternate action variants

Two alternate action designs exist. One design (seemingly older) is a direct clone of SMK J-M0404 alternate action,[2] while the other is a simplified design whose latching mechanism is exposed at the top to the ingress of foreign objects. Both types are notable for being illuminable: slots that run through the switch from top to bottom allow an LED with long legs to be fitted, reaching all the way down to the solder side of the PCB.


  • 1KB101ATUS (USw LXBB01, LXRB01; 1987)
  • Some Apple II clone keyboards[2]


SMK J-M0404 mount

The following switches appear to be SMK J-M0404 mount.

Cherry MX mount

The following switches appear to be Cherry MX mount, and come from the 1KB101ATUS keyboard.