All photos on this page were taken by Michael Summa in the 1970's-80's. The one above was on US 287 NB in 1979, the one below were taken in 1976, and the one to the right was taken in the 1980's, northbound near I-80 on the locally maintained half of WY 222.
Not sure if this was ever standard for Carbon County or Wyoming counties in general, but I highly doubt you'll find another shield like it anymore. It was found just off of I-80.
WY 92 begins at US 85 and heads east, with the number continuing to Illinois; taken in 1979. Then in the mid-1980's, WY 221 EB in the Cheyenne area, demonstrating the end of black-on-white banners (they now match the shields' colors).