There is no photograph to see your truncheon but, the Aux-Units were issued with such a device, hard black rubber, around 13 7/8th. long by 1 1/4" diameter and a transvers hole about 1 1/2" from the end for attaching a cord loop. The ends should be chamfered to 1/8" x 45 degrees. Some folk have stated that these were manufactured between the wars for riot control but I can find no positive information to confirm this. I do believe that these were made purely for Aux-Unit use early in 1940. One at Parham has been grooved at the grasping end for a more secure hold. These coshes were not simply used for hitting, pressure points were tought that resulted in paralysis and death. If your truncheon fits these dimensions, you have a very rare item. Talcum powder or French chalk rubbed into the surface will prolong its life if it shows signs of ageing. Rubber by design, will eventually degrade, chalk will extend its life.
I would welcome opinion on this Rubber Truncheon Cosh. I have been told it may have belonged to a member of an Auxiliary Patrol, however I have no way of proving it. It seems to have age and is some 15 inches long and about one and a quarter inches in diameter. It has a marking on the side which states The "Stunner". It could of course be pre- WW2, WW2 or post- WW2, Civilian, Police or Military. I would welcome comment and opinions. Regards, Clive.