mid or late 1980s.

I haven't spent much time researching the history of plastic chips as much as I have spent researching the history of the clay chip molds. There are some people who post or visit this forum who know more about this history than I do, but since Michael mentioned my name, I will share what I know or think I know.

Those high quality plastic "Langworthy" chips were first made by R.T. Plastics. RT Plastics was incorporated in 1980, although I think based on a newspaper listing that they were producing some type of plastic chip by 1979. Their factory and office was originally in Venice, California.

Don Jarchow and Joseph Fabrizio purchase the Langworthy Co. (Las Vegas, NV) around 1985, and they developed a close relationship with RT Plastics, who sold them the plastic Langworthy chips. I would guess that those chips first appear around the mid/late 1980s, but I have not looked into it closely. Using the ChipGuide it should be possible to more precisely date how early those chips show up.

In 1995, Joe Fabrizio purchased RT Plastics, and moved the company to Las Vegas. I suspect that he had some type of financial connection to the company long before that. The company goes on to make more complex and protected plastic chips.

Hard to date when that type of chip was no longer sold by RT. At some point it was copied by a Chinese manufacturer, and produced in the millions. They were everywhere and anyone could hot stamp them. If I recall correctly, one difference with the Chinese chips was that unlike your chip, the three pairs of double stripes did not always match up (align) with the spots in the interior ring.