The earliest reference that I have for this device is a U.P. press release from January of 1951. The relevant sections follow:

"Navy Develops Atom Detectors . . . Dog Tag Devices Test Radiation." "Silver-activated phosphate glass is the sensitive element in the second type[of dog tag device]. Gama [sic] rays turn the glass to an orange color under ultra-violet light. The navy said a quick measure of radiation intensity can be made visually and that a more accurate measurement can be determined by a simple and compact photo-electric "reader.""

Ten years later, in October of 1961, an AP press release featured a photo of a woman holding a DT-60 dosimeter. The accompanying text read: "Nuclear Neckwear. Linda Bromley of New Rochelle, N.Y., holds in her left hand a personal radiation detector whose maker says could be the next thing in ladies neckwear should the threat of nuclear fallout increase. The lead shield plastic-covered detector, called a dosimeter, is the size of a half dollar and weighs one and a half ounces."

The DT60 was produced for the military by a variety of manufacturers: Bausch and Lomb Optical Co., Penberthy Instrument Co. Inc., Corning Glass Works, and Polaroid Corporation. The DT-60B/PD was manufactured by Speciality Electronics Corp. and the Model DT-60C was manufactured by Industrial Electronic Hardware Corp.

Donated by Ron Kathren and David Bullock

References

RADIAC data sheet.

Department of the Navy Directory of Radiac Equipment NAVSHIPS 94200.5, page date April 1958.

Defense Nuclear Agency List of Military and Civil Defense Radiac Devices HQDNA(AR)-124 3M, August 1987.

Ron Kathren, personal communication.