Here's a couple of sources about plaques and jetons --
From the ChipGuide: the B&G page, showing various sample plaques. Some with "lunettes" (the translucent circular "windows" embedded in the plaque. Also, some of the various materials that cover the plaques.

http://chipguide.themogh.org/cg_chip2.php?id=FRXXBE&p=00110&v=113411661#180

For a history of B&G, see this "History" page on the GPI website. B&G is part of GPI. Note that since GPI became a private company, some of their picture links aren't showing up on the webpage now.

https://www.gpigaming.com/company/history