Battle Relic: Luminous
Marker Disk, US Army, World War
Two Introduction: Battle
Relic # 13 is not about one
specific and unique item, but
describes a feature of a mass
produced and widely distributed
little device used by Allied
forces in World War Two. This
file focuses on the question: "Are
the Luminous Markers, Type I,
really radioactive; even today?".
These markers consist of a
transparent Plexiglas circular front
(the 'window') which is attached to
a black metal circular back.
The 'window' has a 'bubble' in the
center containing a yellowish-white
There are several variations of the
device, such as
unmarked British-made disks and
types that can be attached to
equipment by means of a
The disks were originally designed
to mark roads and were produced for
the US Corps of Engineers.
The powder inside the disk could be
charged by holding it close to a
In several publications, mostly
on-line discussion forums, the story
has it that the light emitting
disks, used in World War Two to mark
routes, equipment and even soldiers,
still release a dangerous amount of
So far, we were not able to find
convincing results of a valid
radiation test of these markers.
Actually, we were under the
impression that after more than
sixty-six years the radiation must
have decreased dramatically.
This assumption was supported by our
modest experiment of looking at one
of these markers in a blacked-out
It did not show any more brightness
than a white sheet of paper.
Incidentally, the marker disks have
been the subject of some other
controversy in the past.
Because the American-made markers
have the warning "POISON INSIDE"
stamped on their backs, it was
assumed that they were in fact
deadly capsules with poisonous
powder inside the Plexiglas bubbles,
issued to secret operators in the
Office of Strategic Services (the
predecessor of today’s Central
The persistent online remarks about
the danger of these gadgets, often
associated with US paratroopers on
D-Day, triggered our wish to end the
These pictures show several disks,
their metal container and the
instruction for use.
The instruction sheet reads:
DIRECTIONS FOR STORAGE,
HANDLING, AND DISPOSAL OF
MARKERS, TYPE I
1. AS MANY AS 3 LUMINOUS
MARKERS MAY BE WORN ON THE
WITHOUT HARM TO PERSONNEL.
2. ONE BOX OF 24 MARKERS
MUST NOT BE CARRIED ON THE
PERSON FOR PERIODS IN EXCESS
OF 8 HOURS IN ANY ONE DAY.
3. PERSONNEL EXPOSED MORE
THAN 8 HOURS PER DAY MUST
MAINTAIN THE FOLLOWING
TABU-LATED DISTANCES FROM
QUANTITIES OF THE MARKERS:
NO. OF BOXES (24 PER BOX) DISTANCE FROM PERSONNEL
2 TO 50
2 TO 50 4 FEET
50 TO 300
50 TO 300 8 FEET
300 TO 1000
300 TO 1000 20 FEET
4. RADIOACTIVE MATERIAL
FOGS FILM. – IN
QUANTITIES OF 100 BOXES OR
LESS A SEPARATION OF AT
LEAST 100 FEET MUST BE
MAINTAINED BETWEEN FILM AND
FOR GREATER QUANTI-TIES THE
DISTANCES MUST BE IN
PROPORTION TO THE QUANTITY.
5. PERSONNEL SHOULD BE
CAUTIONED AGAINST TEMPERING
WITH THE MARKER OR IN ANY
WAY EXPOSING THE LUMINOUS
COMPOUND. BROKEN OR DAMAGED
BUTTONS SHOULD BE DISPOSED
OF BY BURIAL OR BY CAREFULLY
WRAPPING, MARKING THE
PACKAGE AND RETURNING TO THE
DEPOT FOR SALVAGE AND
DISPOSAL. IF ANY LUMINOUS
COMPOUND ACCIDENTALLY COMES
IN CON-TACT WITH THE BODY
CONSULT A MEDICAL OFFICER.
Two disks were borrowed from private
Both are of the American type with
'just' grommets for attachment
We discovered that varieties with
clip and pin back attachments are
scarcer and therefore more
One disk was in mint condition, the
other one had a crack running along
the Plexiglas 'window' and its
powder containing 'bubble'.
(click to enlarge)
A radiation expert, working with the
Regional Health Aid Organization
(abbreviated GHOR or Geneeskundige
HulpOrganisatie in de Regio in
Dutch) in Eindhoven (The
Netherlands) was willing to put
these two disks to an Alpha and
Gamma meter test.
His job is to measure radiation
values in suspected locations before
fire fighters or policemen enter the
scene of a fire, environmental
accident or clandestine narcotics
The results are eye-opening!
We suggest viewers to watch this
(direct link: https://www.youtube.com/watch?v=0L8mOjjFJJ0)
At the time
indication of 0:09 in the video the
radiation expert can be heard
"When you are exposed to this
amount of radiation for ten hours,
you have had your yearly dose!"
We were told that the disks are
emitting so called Gamma-rays.
The biological effect of these rays
is expressed in "millisievert" (1
mSv = 10−3 Sv) and "microsievert" (1
μSv = 10−6 Sv) per amount of time.
It is advised that an average person
should not be exposed to more than
2.4 millisievert of natural
background radiation (from cellular
phones, electronic devices,
etcetera) per year in order to avoid
a higher chance of getting cancer.
The experiment included measuring
the radiation emitted by the
individual disks, by both disks
stacked, by the disks inside a
plastic container and with a metal
(aluminum) sheet over the plastic
An Automess 6150 "tempo meter" or
"dose meter" was used to conduct
After an initial test with only the
meter, a measuring probe was
attached and the amount of radiation
was measured again.
The meter produced a few short
beeps, increasing in frequency to
end in a constant warning tone
indicating a hazardous dose.
The individual disks emitted an
amount of radiation between 120 and
140 μSv per hour.
The stacked disks emitted an even
higher value than a single disk:
in this case 207 μSv/h .
The radiation expert was able to
pinpoint both disks inside the thick
plastic container just by hovering
the dose meter over it and listen to
the increase of bleeps.
A metal plate of a few millimeters
thick did not stop the radiation;
although it then was of a lower
(click to enlarge)
(click on the
thumbnails to enlarge)
The expert went on to explain that
he had held the meter in close
proximity of the tested disks.
Keeping the disks inside a thick
metal box and maintaining a certain
distance are remedies against too
much exposure to their radiation.
He advised against keeping the disks
close to (a) person(s).
It has now been well established
that the Luminous Markers, Type I,
are in fact radioactive; even today.
They emit a dose of radiation which
can be hazardous to the health of
The advice in the World War Two
dated instruction sheet, stating
that up to 3 disks can be worn on a
person indefinitely without harm, is
therefore not true.
We advise viewers who own a device
as described here, to keep a safe
distance from it and / or to keep it
stored in a metal (preferably thick
lead) container should one desire to
continue owning it.
Although often associated with
American airborne troops deployed in
the night before the Normandy
invasion on 6 JUN 1944, there are
few period photographs to justify
labeling the luminous markers as a
typical airborne item.
In several of the excellent books by
Belgian author Michel DeTrez the
luminous disks are depicted as in
integral part of the individual
equipment of the American
(click to enlarge)
We did however find these images of
Lt-Col Michaelis, executive officer
of the 502nd Parachute Infantry
Regiment, in the marshalling area
prior to the D-Day drops.
He seems to be wearing a luminous
disk on his helmet.
Given the results of our experiment,
this is a very unadvisable practice.
The pictures below may show that
"Iron Mike" only carried a disk on
his helmet for a limited amount of
(click to enlarge) 1
Picture 1 and 2 were
taken in England prior to D-Day,
picture 3 was presumably
taken during his deployment in
Normandy and picture 4 shows
Michaelis on his return in England
in July 1944. On neither one of
these pictures he is seen wearing a