I tried to do some rudementary research, but without more work it is hard to know if the current owner is the original owner, or just a corp with the same name. I caught ISC as one of these abandoned domains, there may be more.

Oldest Domains:

1. Symbolics.com => Domain Squatter

2. BBN.com => Owned by Raytheon

3. Think.com => Owned by? Oracle

4. MCC.com => Domain Squatter

5. DEC.com => HP.com

6. Northrop.com => Northropgrumman.com

7. Xerox.com

8. SRI.com

9. HP.com

10. Bellcore.com => Telcordia.com

11. IBM.com

11. Sun.com => oracle.com

13. Intel.com

13. TI.com

15. ATT.com

16. GMR.com => Broken?

16. TEK.com

18. FMC.com

18. UB.com => ultimatebet.com

20. Bell-ATL.com => verizon.com

20. GE.com

20. Grebyn.com => broken?

20. ISC.com => Aquired by Kodak who abandoned domain

20. NSC.com

20. Stargate.com => latisys.com