It looks like that because its 2 pieces of plastics molded together.
It's very durable to wear; and the text comes out very clear compared to other key print types e.g. laser etch which is slightly fuzzy n dirty.
This is my limited geekhack dolche double shot injected 104 key set


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# Material ABS.
Source.# Font Modified Arial (rounded).
Source.# Labeling Technology Double Shot
# Weight .8g
# Front Edge Thickness .8mm
# Other Notes Signature DCS profile is a bit higher than Cherry and a bit lower than Filco. Filco on top row, Cherry Corp in middle, Signature DCS profile on bottom.

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Key Materials and Key Wear
There is a bewildering array of plastics available and when you add in the different additives for softening, the ability to mix plastics, and fire retardants it's not easy to generalize how keys will wear. In addition, keyboard manufacturers generally will not advertise what materials they use in keys and focus instead on cost cutting. These are some of the plastics you may find to be in use:
PS, PC and PVC (Polystyrene, Polycarbonate, Polyvinyl Chloride). Common and cheap. This is a lighter less durable plastic that tends to be vulnerable to solvents. Most keyboards shipping today including Logitech, Microsoft, etc. use some variant of this for their casings and keys.
ABS (Acrylonitrile Butadiene Styrene). It's commonly used for older keyboard casings. It's a comparatively soft material compared to some modern plastics but is resistant to breakage. Topre casings are made of ABS and probably most IBM Model M's are as well. Although I am not sure I suspect Filco and Das keys are made of ABS.
PBT (Polybutylene Terephtalate). PBT is a common choice for modern Cherry keycaps and is what IBM and Unicomp use. It should not yellow as much as ABS over time.
POM (Polyoxymethyleneor better known by the brand name "Delrin"). An abrasion-resistant and low-friction material, this found use in older black Cherry G80 keycaps. However it is expensive and not common in other keyboards.
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Labeling techniques
Applying key labels can be done in a number of ways:
Two-shot injection molding is one of the best variants and used to be common with high-quality keyboards. Here the keycap (keytop) has cavities which are filled with differently-colored plastic of the same type during production. This allows for contrast-rich labeling, even wear and high wear resistance in general.
Another method is dye sublimation which appears to be used on two-piece IBM keycaps (as well as old Cherry S... keycaps). As noone has complained about wear on these so far, this seems to give good durability as well, or at least may do so provided the base material does. Apparently a certain degree of heat resistance is required, favoring the use of keycap materials which are less susceptible to wear as well.
Laser engraving became popular in the mid-1990s. This also tends to have good wear resistance, but contrast isn't very high.
Pad printed (tampo-printed or silkscreened) lettering may also give good contrast, but tends to be subject to wear.
Some manufacturers have tackled the problem of wear by using a rather ordinary labeling method but coating the result with some more durable transparent plastic - examples would be the "decals" found on Chicony and inexpensive Logitech boards (just the lettering itself covered) or the entirely coated Filco keys.
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http://geekhack.org/showwiki.php?title=All+About+KeysThis post has been edited by Moogle Stiltzkin: Dec 10 2010, 01:22 AM