I'm only aware of one such four-way traffic signal in Oregon, located in St. Helens at the intersection of Old Portland Road and S. 18th Street. Are there any others still in existance anywhere?
I know in Washington that there are a few in Chehalis and in Seattle's Pioneer Square district...
Washington has a four-way flasher at the junction of old US-10 and old US-395 in Ritzville.