H2Oxide----correct on both guesses in that 552nm can be produced both ways! Very accurate intuitive sense of laser wavelength generation possibilities.Any idea what it is? My guess would be OPSL or an uncommon Nd doped crystal (doubled of course).
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