Record Technology Incorporated, RTI, have pressed several Nirvana reissues, among them the first Original Recordings Group reissues and Sub Pop's 20th anniversary reissue of Bleach. Metal plates processed by RTI are marked with an internal job number followed by side and processing method information . As an example Nevermind (ORG-032) has the numbers "18200.1/2(3)". The numbers seem to be handwritten into the lacquers before plating, due to smoothness and depth. These numbers do not necessarily determine that the record in question was pressed by RTI, only that they processed the metal plates.
The final number, inside the paranthesis, can be either "2" or "3". It identifies whether the metal plates have been processed using their two-step or three step processes.  Both processes start with creating a set of fathers from the laquers. In the case of the two-step process, a set of mothers is then created from the fathers, and once the set of mothers has been evaluated and approved, they use the set of fathers to press records directly. This is quicker, but only feasible for smaller quantities, as more mothers cannot be created once the fathers have been used to press records. A finite amount of additional stampers can be plated from the mothers. In the three-step process, the fathers are not used for pressing, instead they are used to create more mothers, if needed. Only stampers made from mothers are used for pressing. The three-step process is used for larger quantities and high-quality heavy-weight pressings. 
There is a quality difference between the two. In the two-step process, the lacquers are first pre-plated at low temperature and amperage before they are moved to a rotary tank at a higher temperature and amperage. In the three-step process the laquers are not moved to a rotary tank, but left in the original tank much longer. This improves the quality, but is a much slower process. 
According to their website, RTI will usually deliver five test pressings of standard weight pressings, and ten test pressings of high-quality pressings. Additional test pressings can be made upon request and with additional payment. 
The remastered Bleach 20th anniversary 2LP reissue (SP 834) was pressed by RTI on heavy-weight vinyl. They also pressed the single LP reissue (SP 034) on black regular weight vinyl. Around 2011, when they were going to press a batch of the black single LP records, RTI accidentally pressed some on white vinyl. They were packed in single LP sleeves, sealed, and "white vinyl" stickers were put on. About eight to ten copies were pressed before they caught it. None of them were sold.  Judging by the weight of the sealed record, it seems to be on heavy-weight vinyl.
The heavy-weight and regular weight pressings have different matrix codes. As this mispress appears to be heavy-weight, the matrix codes are most likely the same as those on the first disc in the 2LP release.
1. Bleach SP 034 white vinyl mispress, front of sleeve with stickers