Short answer, yes.
Long answer, much like old highway/road signs I am much more familiar with, these porcelain signs do not meet US Forest Service Standards and were taken out of service. From what I have seen the USFS will often defer to Manual on Uniform Traffic Control Devices (MUTCD) on signing and specifically for mileage/directional signs. MUTCD has very specific guidelines on size, color and and materials and this sign doesn't meet any of those
I'm not an expert on these, but that is just what I've read when researching some of my highway signs. It is so nice someone saved this from going to landfill, were so many of them were sent once they were replaced.