Early production of the 725 series was done in the United States. Switches produced within the United States can be identified with a single round eye. See NMB First Generation of keyboards for more information.
White Gundam - US Made
Carcol Gundam - US Made
After a couple of years, the molds for the 725 series was retooled. The "Soap Dispenser" also known as "Gundams" was replaced with a more blocky style of slider. Production of the 725 series was to moved to Thailand. Moving production takes a lot of time and during the transition period, it's believed that new molds were also produced in the United States.
Grey Linear - US Made
White Linear Thailand Made
The new molds in the United States still share the round eye but with the new blocky slider. These new blocky switches that are produced within the United States have been found both in First Generation and Second Generation keyboards.
The reasoning behind this might have been that the new tooling being produced in Thailand could have gone through numerous tests and revisions. Once the new factory in Thailand was producing switches the United States switches stopped production. The switches that started production in Thailand would bear the new square one eye.
Series 725 switches are notable for having a particularly unusual keycap mount — the slider is large and flat-topped and the keycap clips over the top. The return spring reaches to the top of the slider, meaning that the keycap sits over and around the slider, reducing the height requirement of the keyboard significantly while retaining full travel (the switches are specifically patented as "low profile"). As a result, there is no upper shell, as the slider also serves this purpose.
Like the previous Hi-Tek High Profile switches, the slider contains a horizontal plastic bar that holds apart a pair of vertical electrical contacts, which close together when the slider is depressed or removed from the switch. Each contact has two legs, for a total of four arranged in a square. The legs are press-fit into the lower housing.
The movement of the slider is controlled by a central tr-lobed guidepost in the lower housing which slides within a matching cavity in the slider. This post allows a vertical sliding motion while preventing any rotation. A center bore in this guidepost locates the spring and prevents buckling. A small lug in the slider provides a seat for the upper end of the return spring to prevent lateral movement. The slider is retained in the lower housing by a set of flexible tabs on the slider which fit into slots in the lower housing.
(See link for more variations above)
The Series 725 switch was designed as a linear type and commonly found in early keyboards as well as those used with computer terminals.
(57.1 +/- 14.2 grams)
The tactile variant of the Series 725 switch is the least common of the three standard types.
Tactility is provided by the contact leaves. The contact leaves have an indentation on each arm which narrows the spacing between the two contact arms. As the slider is depressed, the contact separator bar moves through this narrowing, pushing the contact arms apart before allowing the contacts to touch. This spring of the contact arms provides increased resistance generating tactility on both the down-stroke and upstroke, with the upstroke being slightly more pronounced. The contact separator bar within the slider is narrower than that of the linear variant. The return spring of the tactile variant is slightly shorter and has fever active coils than that of the linear version.
The clicky variant of the Series 725 switch was introduced in the late 80s and became the most common variant found in later keyboards.
The click is achieved by way of a plastic follower arm that runs inside a track integrated into the rear of the slider. When the slider is depressed, the follower or click arm travels up the track and over a ramp creating an audible click sound. This follower arm is plainly visible and accessible without needing to dismantle the switch. This arm also provides a small amount of tactility. in order to add the track added to the slider, the rear portion of the central guidepost in the lower housing had to be flattened on one side. The click variant uses the same spring and contact arms as those used in the linear version.
(75 +/- 10 grams)
The latching or alternate action variant of the Series 725 switch is uncommon, only being found in a few earlier keyboards. The latching mechanism consists of a pivoting latch arm mounted in the lower housing that runs in a one-way track in the slider. The track design is heart-shaped and incorporates a series of ramps to ensure the latch arm is only able to travel in one direction. Once the switch is depressed, a central v-shaped block traps the latch arm in the depressed state. Pressing the switch a second time forces the latch arm to continue the one-way path and return to the released position. This heart-shaped track design is similar to that seen in other latching switch designs.
Latching Switch Latched
The spacebar variant exists as linear, tactile, and clicky versions.
They are identical to their standard counterparts of the same type other than the spring. The spring used in the spacebar variant is longer which results in an increase in the force required to depress the switch. These switches are often marked with a painted dot or different colour, presumably used to differentiate them from standard switches during production.
(85.6 +/- 14.2 grams)
The integrated LED variant of the Series 725 switch integrates a 3mm round LED into the lower housing that is visible through a circular window in the keycap. The LED can be physically located in either the NE or NW corner of the switch, but the only known windowed keycaps use the NE position. To accommodate the LED, the slider was designed with a tapered shape. Linear, tactile and clicky versions of the integrated LED switch exist.
(57.1 +/- 14.2 grams)
Model Number Overview
This section is to better provide more in-depth context around keycaps produced by NMB.
The first generation of keycaps are pressure fit and work on any generation of switches. Fingers within the caps are thick all the way from the center to the outside of the cap. These caps are normally only found on NMB First Generation keyboards and the caps are shiny on all sides.
The second generation of keycaps are clip fit design. Alpha keycaps normally will contain the same fingerstyle as First Genernation keycaps which are thick all the way through the finger. Stabilized keycaps however normally have thinner plastic after the first initial few mm from the inside of the finger. The stabilized keycaps used the wire design where the stabilizer wire clips into the switch housing and the keycap rests on top of the stabilizer wire while being clipped into the switch.
All keycaps within the second generation have shiny sides all around.
The third generation of keycaps are clip fit design. The third generation of keycaps introduced the rod stab design. This new design had many iterations and implementations. The sides of the keycaps in this generation initially started off being shiny but later on, in the generation changed the sides of the keycaps to matte. Along with the later caps in the generation having matte sides the keycaps also dropped the rod stab design for the wire stab that was introduced in the Second Generation.
Fourth / Fifth Generation
The Fourth Generation starts in the Fourth Generation of NMB keyboard where NMB ditched the thick font and changed to a thinner font. These keycaps are rough on all sides and continued to use the wire stab design for all stabilized keycaps.
NMB used many different types of stabilizers over the entire production run of NMB keyboards. This section will overview each type and the system that each one uses.
These are the most used stabilizer option on NMB keyboards. The wire stab system was first introduced in the First Generation of NMB keyboards. These stabilizers use unique switches where a different bottom housing allows the wire to be clipped into the switch while being sandwiched between the plate and the wire clip. The bottom housing of stabilizer switches allows multiple wires to be attached for bigger keys including big enter keys found on AT keyboards.
This system of stabilizers was introduced in the Fourth Generation of NMB keyboards. The wire that is used in combination with clips that are molded into the keycap that needs to be stabilized. This system can be used with the wire stabilizers as they don't need to clip into the switch.
This stabilizer system uses a dummy switch with a cylinder located within the center. This allows a rod that's located on the keycap to slide up and down and stabilizing the keycap. This system is used with the Third Generation of NMB keyboards. This system can be found being mixed in with the Wire stabilizer system.
NMB two different types of plates over the entire production run of NMB keyboards. This section will overview each type and the system that each one uses.
Both plates include a notch cutout on the North/Top of the switch to allow Linear and Tactile clip on the top of the switch from interfering with the plate. Without the notch, for the clip, the slider would not return properly.
This is the main version of plates that are found in NMB keyboards. The plate thickness is 1.4mm. There is black paint is applied to the plate followed by an oil-based coating to prevent rust.
This plate version is only found in the Fifth generation of NMB keyboards. They are RAW steel with a sort of clear coat that is applied to the plate. There are indents in the plate unlike the other version to save on plate thickness and therefore material needed. This plate version is the cost-saving measure for the last generation of NMB mechanical