I have tried every source I can to get raw historical stock prices for certain dates in 1990 with no luck, especially for companies that no longer exist.
Even for companies that do still exist, such as Verizon (which was called Bell Atlantic in 1990), all I found online was adjusted prices. And it isn’t even clear what adjustments they applied. Some show different adjusted prices than others. I suppose you can “unadjust” them if you know what they are adjusted for, but that seems like a wasteful exercise.
I want the raw closing prices on specific dates. For that one I will try contacting Verizon to see if they can give me that info.
But for companies that no longer exist like Nynex or GTE, I can’t find any information at all.
I even tried accessing a database of old WSJ issues for the dates I needed. I can get the issues, but the images are so garbled they are illegible. And I even tried talking to their technical people who informed me it is unlikely they can restore those images.
Yahoo Finance offers both close (adjusted for splits) and adjusted close (adjusted for splits and dividends). They don’t offer the raw, unadjusted close, but for most stocks it’s reasonably possible to reverse engineer the stock split adjustments as long as you don’t have to deal with dividends. Be aware, though, that a spin-off may be treated as a split even though it’s a different animal with different tax effects. I don’t know if you’ll be able to get data for discontinued listings from this source.
A large enough library may have newspapers with stock listings on microfilm or microfiche. That would be a fun project.