colour infrared film

[msa]

I have an old roll of Kodak EIR (E4 process) that was kept refrigerated. Is it good for anything, or just a curiosity piece / collector's item?

Well, the bad news is, it's been about 35 years since E-4 chemistry was produced commercially.

The good news is, Kodak documented hand-mixing instructions for it:

http://www.kodak.com/global/en/professional/support/techPubs/cis111/cis111.pdf

So conceivably it's useful, but it would require a lot of work on your part, and probably isn't worth it for one roll. Either get more before you do this, or give it to someone who still has some E-4 film they want to use and process.