I couldn't let this rest, did some research.
The material was quite probably a Platinum-Cobalt (PtCo) alloy. It was one of the best magnetic materials at that time, but too expensive, thus soon replaced by other materials like Samarium-Cobalt.
This is interesting:
http://www.electronenergy.com/about_us/company_info.htm
Biography of Electron Energy Corporation founder Marlin S. Walmer:
"...An alumnus of Lehigh University (BS 1952) and Franklin & Marshall College (MS 1958), he began his career as a
metallurgical engineer at the Hamilton Watch Company. At Hamilton, he worked with platinum cobalt magnets used in wristwatches. It was this work that laid a foundation for the next 30 years of his pursuit to develop, commercialize, and improve rare earth magnets...."
Very good article about permanent magnets:
http://www.grouparnold.com/mtc/pm_manual_chap_1.htm