ESCONDIDO - Escondido Humane Society employees got a little bit more than they bargained for this week when they went to spay a six-month-old tortoiseshell cat only to discover that 'she' was a very rare 'he.'

The black, orange and white cat, named Phinny - short for phenomenal - is a "rare" tortoiseshell male.

"We didn't realize what we had here until we were getting ready to 'fix' him," said Abigail Rowland, the director of development at the humane society. "(A male tortoiseshell) is so unique, we didn't even check to see if he was a girl."

The large majority of tortoiseshell cats are female because the unusual coloring requires the recessive trait from two X-chromosomes. Males traditionally have only one X-chromosome.

About one in every 3,000 male cats are born with two-X chromosomes, humane society officials said. The genetic abnormality, however, usually causes other complications and deformities that prevent the animal from surviving to adulthood.

"I'm yet to meet a vet who has ever seen one," said Staci Fitzgerald, the director of animal care, who was one of the first to discover the animal shelter's mistake. "It's like they exist, but no one has ever seen one."

Fitzgerald said it was her first time in 15 years of working with the animals that she had ever come across a male tortoiseshell cat - a sort of urban legend of the veterinary world - and that she is now happy to count herself among the limited number of people who have.

"He is really a very unique cat," Rowland said. "I'm sure we will never see one like him again."

At six months and freshly neutered, Phinny is strong, an appropriate size and developing normally, officials said.

Phinny came to the shelter as a stray cat at the beginning of the month, Rowland said, and is now ready for adoption. Officials have said that they expect to find a home for him by the end of the week.

By early Wednesday afternoon, officials had received about a dozen phone calls from interested applicants, although no one had come in to fill out an adoption paper or go through the extended screening process. All applicants must provide a veterinary reference and submit to an in-home inspection by an animal control officer, two requirements not normally part of the adoption process, she said.

Rowland explained that because the breed is so rare, the shelter decided to add the two requirements as a way to help ensure that someone wants to adopt the cat as a pet instead of trying to turn a profit. While the shelter's adoption fee for Phinny is the same rate as all of the humane society's adult cats - $55 - people placing ads to sell male tortoiseshell cats have asked for more than $1,000.

Phinny may seem "financially valuable" to some people, but really he is just one of some 700 cats and dogs at the shelter who needs a home, Rowland said.

"He's a purr-box," Fitzgerald said. "Even though he's rare enough to be king of cats, he's very sweet and affectionate. He doesn't know how special he is."

- Contact staff writer Shayna Chabner at (760) 740-5416 or schabner@nctimes.com.