Counter-etching is a term in lithography, having to do with surface restoration. I suppose it could be applied, figuratively, to the way a serif allows trailing off the letter, back to the surface. I don't know about "compensators" in that context (a "compensator" in the modern printing industry is an element of a web press, which doesn't fit your context at all), but rather than use some contorted phrase with "the first ever means of counter-etching compensation", it seems to me that if the author is playfully applying a modern printing/lithography term to ancient carved serifs, that you could write a synthetic phrase in English. If, of course, "counter-etching" is the right guess.

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Note added at 2 days21 hrs (2015-04-13 12:28:37 GMT)
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Thinking about it some more, it occurred to me that if "counter-etching" is correct, then the "compensators" could be generalized to "technique" - "the world's first counter-etching technique."