There's a pretty old FREEWAY ENTRANCE sign on the Banfield.

As stated, Washington does use FREEWAY ENTRANCE signs, but they generally don't include any shield at all, mainly because it's extremely redundant. For routes that aren't exactly freeways, they use EXPRESSWAY or HIGHWAY. Idaho uses them, I think.
Nevada and Arizona use similar road hardware as California, so it's sort of expected that there are some similarities in their signing practices. Arizona uses more MUTCD legal exit tabs; however, both Arizona and Nevada neuter and black-box their shields.
Has anyone seen the on-ramp from Exit 8 on WA-16? I'm curious how Washington deals with tolled roads... Here's how California does it (without the black pricing tags):
