'Extremely rare'

Mr Roy got an electric shock while repairing a high voltage wire last October.

The doctor who treated him insists that his patient underwent an extremely rare medical phenomenon.

"When he came to us late last year, his scalp was completely burnt and within months it came off, exposing the skull," surgeon Ratan Lal Bandyopadhyay told Reuters.

"Later, we noticed that the part of his skull was loosening due to lack of blood supply to the affected area, which can happen in such extensive burn cases."

Correspondents say hundreds of people have now gathered around Mr Roy's hospital bed to see him holding his extraordinary trophy.

Dr Bandyopadhyay said the skull's inner covering and the membrane which helps produce bone were "miraculously unaffected", allowing fresh bone to grow.

"When the skull came off, I thought he will die," the doctor told Reuters, "but we noticed a new covering on his head forming and that might have pushed the 'dead skull' out."

Doctors say that 80% of the outer part of Mr Roy's skull has now hardened, and they expect him to be completely cured in about three months' time.

Scalp or skull?

But some experts say that while such a development is possible, cases are extremely rare.

"It's most likely that the hard outer portion of the scalp came off," a senior orthopaedic surgeon in Calcutta - who does not want to be named - told the BBC.

"If the skull itself came off with the brain of the patient being exposed, the patient wouldn't have survived."

Another surgeon, Mrinal Kanti Biswas, pointed out that no X-rays had yet been carried out on the patient.

"Before scientific tests are conducted, it wouldn't be proper to comment what exactly came off - whether it is the skull or the outer portion of the scalp," he said.

Prized possession

Mr Roy is in no doubt that his is a fantastic tale of survival.

"Doctors say a new skull covering has replaced the old one, but I am not letting go of this one," he told Reuters.

He said that he intended to keep his prized possession for life and not hand it over to the hospital when he left.

"My skull has made me famous," he said.