Identified only by a small stamped "3" in the runout. The double/outlined diamond is not a pressing plant indicator.
This plant operated from 1939 to 1957 (but was idle between 1948 and October 1949). Mercury Records purchased the plant in May 1958, renaming it National Record Pressings, Inc. It eventually became Richmond Record Pressings, Inc. and then Mercury Record Manufacturing Company when it was closed in Dec 1969. Ultimately replaced by Philips Recording Company, Inc. which officially opened Apr. 1970.
For releases with a solid diamond (◆), please use Decca Records Pressing Plant, Pinckneyville - do not confuse them! The outlined diamond (◈) was also used on labels provided to other contracted pressing plants (such as RCA Records Pressing Plant, Indianapolis) and other Decca plants such as Los Angeles or Gloversville (at the end and beginning of their service, respectively).