An anonymous donation has reunited Bovington Tank Museum with an item that was pinched by a young soldier 40 years ago.

The apologetic letter which accompanied the mystery package on its arrival at the Bovington museum said: “In the late sixties I was a member of the Junior Leaders Regiment RAC and remembered obtaining an instruction plaque from inside Tiger 131. “Recently while clearing my loft I found the plaque.

“I collected cap badges and memorabilia while I was at Bovington and I bought this off one of the lads.”

The plaque, 25 x 20cm of embossed zinc alloy, is entitled ‘Bedienungsleiting fur Turmabdichtung’ and gives instructions for the waterproofing turret. Tiger Tanks had been designed to cross water obstacles like rivers by literally wading through them – and they could be prepared in such a way as to be completely immersed in water with the addition of a long snorkel.

Chris Copson, the museum’s education officer, who translated the plaque, said: “The instructions run the crew through the process of preparing the tank for complete immersion in water, ensuring it is done in the right order.”

Back in the 1960s the highly successful but now defunct Junior Leaders Regiment was based across the road from the museum, recruiting and training school leavers prior to their joining the regular army as Non-Commissioned Officers.

After hours the museum was too much of a temptation among the bored teenagers, some of whom would illicitly gain access to cause a little mischief and, if possible, acquire the odd souvenir.

“So the story goes, it was a previous curator who invented the story of ‘Herman the German’ – the ghost who haunted The Tiger Tank – in order to keep the boys away from the museum at night,” said Chris.

‘Herman the German’ has since become one of the most enduring myths associated with the Tank Museum but it evidently did not deter one young souvenir hunter, who according to the letter: “Got into the tank as the top hatch grill had been left off.”

The letter concluded: “I hope you can reinstall this item from where it came, or at least use it to understand how the waterproofing was carried out.”

The instructions guide the crew through securing the turret, removing the coaxial machine gun, retracting and locking the gun sight before insert sealing plugs and placing waterproof covers over air intakes.

“Whoever this donor is we are extremely grateful for his thought and kindness in returning it to us and can assure him that the plaque will soon be back in its rightful place,” said Chris.

The Tiger Tank will be in action tomorrow, taking part in the museum’s inaugural Wartime Military Vehicle Show.