I have played a lot with different readers like Kaywa, Quickmark and some from Japan. They all more or less the same.
iMatrix (according my own experience) has one important feature - it stores codes locally and can regenerate them on screen making device ready for ticketing, couponing or loyalty applications.
Particular readers are not so interesting, but features they offer beyon reading are vital, as well as implementation od as many proprietary services as possible.
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