Pallas pressed the Nirvana reissues released on ORG Music from late 2010 and on. Before that, the ORG releases were pressed by Record Technology Incorporated (RTI) in the USA.  The change of pressing plants can be explained with some knowledge of ORG.
There are two different companies, or brands, connected to the ORG name. The company was started in late 2006 as Original Recordings Group, or simply ORG. ORG Music seems to have been created in late 2010. Both these labels coexist today. ORG Music seems to deal mostly with rock/ contemporary music, while ORG deals with other genres. 
Nevermind (ORG 032), In Utero (ORG 033), and Unplugged In New York (ORG 034) were all originally released on ORG in 2009, pressed by RTI, but transferred to ORG Music in late 2010.  New pressings were made of all three albums by Pallas, and Incesticide (ORGM 1005) was also released. The three first records were given ORG Music catalog numbers on their official website, for example ORGM 032, but this was not reflected on the actual new pressings, which kept the original catalog numbers, in this case ORG 032.
In 2009, prior to pressing the Nirvana records, ORG either became a division of or went into a partnership with Warner Bros Records. The ORG Music website states that the company is signed to Warner Bros.  It is this relationship which utlimately determined which pressing plants were used.
The main pressing plant used by Warner Bros was RTI . As mentioned, the original 2009 ORG pressings of Nevermind, In Utero, and Unplugged In New York were pressed here . However, RTI was at the time overwhelmed by demand, and Warner Bros had approached Furnace MFG for supplemental capacity well before the original Nirvana records were pressed .
Furnace MFG is an American broker which subcontracts the various parts of the production to other companies. Their orders are pressed by Record Industry in Holland and Pallas in Germany. These partnerships are referred to as Record Industry USA and Pallas USA.  Warner Bros started having the releases on the newly formed ORG Music records pressed through Furnace some time in late 2010 (at least in Nirvana's case) .
The new ORG Music pressings where pressed with stampers made from the mother plates originally processed by RTI for ORG, as seen from the matrix codes. Before they processed new stampers, Pallas stamped their internal job numbers and "P. USA" to indicate that the records were manufactured through the Pallas USA partnership. The rest of the matrix codes are obviously identical to the first pressings by RTI. Warner Bros may still also have used RTI to process mother plates for new releases.
P. USA (on records pressed through Furnace MFG)