Place of manufacture for DEC equipment?

A simple rule to remember: DEC originally had two-letter site codes. When they used them all up, they switched to three letter codes, and converted all existing two letter codes to three letters by appending ?O?. So if it ends in O, it was originally a two-letter code; if it doesn?t (like SHR) then it was created after the change and it doesn?t have a two-character equivalent. I don?t remember that ZK was ever a manufacturing site so I wouldn?t expect to see it in a serial number. Along the same lines, there was Merrimack, NH: MK(O), also a software engineering site. There were at least two other Nashua locations, one of which was Nashua CSS; I don?t remember the site codes for either (NU, perhaps?). The CSS site might show up on serial numbers of CSS oddball stuff (the DX11 for example, if it was built at that particular CSS facility). I wonder if I still have a DEC phone book buried somewhere... paul