Any idea what it is? My guess would be OPSL or an uncommon Nd doped crystal (doubled of course).
H2Oxide----correct on both guesses in that 552nm can be produced both ways! Very accurate intuitive sense of laser wavelength generation possibilities.
Industry leader Coherent announced a 552nm OPSL laser in January 2011 see: https://www.coherent.com/investors/index.cfm?fuseaction=Popups.ViewRelease&ID=892
The CNI 552nm however is a DPSS Laser ---presumably lower cost than OPSL units and of a type similar to the 2012 work quoted above
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