Sky News has learnt that Stanley Gibbons, one of the collectibles industry's most prominent names, is working with advisers to attract new investors.

City sources said an outright sale was a possibility, but that a number of options were being explored.

PricewaterhouseCoopers, the accountancy firm, is overseeing the process.

Stanley Gibbons traces its roots to 1856 and claims to be the world's oldest rare stamp merchant.

The company's eponymous founder was born in 1840 - the same year that the original Penny Black was issued.

It has held a royal warrant since 1856, and had been a publicly traded company for just over 20 years before its delisting.

The move to take it off the stock market was engineered by Phoenix Asset Management, its controlling shareholder, which had warned that its ongoing financial support for Stanley Gibbons would be in doubt unless the delisting was approved.

It was unclear on Monday whether Phoenix wished to retain a stake in the company.

In a statement, Stanley Gibbons said: "On the back of a strong performance this year across the business, we are now seeking fresh investment to support our growth plans and the innovation of our services to meet the needs of today's collectors.

"This is a positive development for the company but we are unable to comment further at this time."