older LPs - different EQ?

After seeing 35,000+ LPs in one place on Sunday, including a wide variety of selections from the early years of recorded music, I suddenly remembered a foggy thing that I read a while back, and I want to confirm.

My impression is that pre-1958 or so (1955?) the record companies used a different equalization curve than the now-ubiquitous RIAA equalization. Is this true? If so, what sort of phono stages do equalization for these properly? Anything else to be aware of in this space?