The details of the original OSCAR-Locator was first described by it's creator, Kay Deskur, K2ZRO (SK), in an article in the 73 magazine issue dated July 1975. K2ZRO called it "Satellab".
Since the 73 magazine is now in the public domain, electronic issues are available on the web. Look for the July 1975 issue at: https://mikeyancey.com/73mag/index.php
This 73 magazine article was reprinted in the March 1976 AMSAT Newsletter. It's available on Phil Karn's web site at: http://www.ka9q.net/newsletters.html
For production quantities of the device, now called OSCAR-Locator, I think AMSAT might have made some. I say this because the version I have (which is of very good quality) has K2ZRO printed on it and AMSAT's name and address.
Later, The ARRL also sold their version. The ARRL printed updated ground tracks in QST for any new satellites that were launched.
OSCAR-Locators and Satellab all basically worked the same.