Ortofon A/S, Stavangervej 9, DK-4900, Nakskov, Denmark. Tel: (45) 54-91-19-15. Fax: (45) 54-91-19-11. Web: www.ortofon.com. US distributor: Ortofon Inc., 500 Executive Boulevard, Suite 102, Ossining, NY 10562. Tel: (914) 762-8646. Fax: (914) 762-8649. Web: www.ortofon.us.
The Beyer (now Beyerdynamic) DT-48 headphone was first made in 1937 and is scheduled to be discontinued this year, with a 75-year run. I don't know about availability during that entire time, but there it is.
Ironically, I was made aware of it from Stereophile's Recommended Components in the early 1970's.