Given the recent run-up in the stock market and spike in interest rates, investors are rethinking where the best returns on their money can be found. While the traditional avenues such as stocks, bonds and cash will always be perennial favorites, more and more investors are looking to diversify their holdings and smooth out their returns in lesser known places, which is exactly where Londoner Nick Salter comes into the picture.

"At the end of the day, stamps are an alternative investment," the founder of the Philatelic Investor says in the attached video. "Just like wines, or classic cars."

While he acknowledges that this sticky asset class should only count for a "small proportion of an overall portfolio" he says the long-term returns are first class.

"Very broadly, over the past 40 years, net returns have been in the region of eight to 12-percent," he says, adding that only a tiny percentage of all the stamps that are collected can be considered investment grade. "A good 90% of all stamps are only of worth to the collectors themselves."

Because stamps have "universal appeal" he says demand continues to go up, especially in growing nations like China, India and Brazil, which is of course driving prices.

To date, he says the single most valuable stamp in the world is believed to be the $2.3 million Treskilling Yellow --a rather ordinary looking gold-colored stamp from Sweden that was misprinted in 1855 and believed to be the only one of its kind.

Clearly, dabbling in rare stamps is not for the uninitiated.

"You're dealing with very small pieces of paper, which are worth an awful lot of money," Salter says, "and because they are, there's been a great temptation over the years - and there still is today - to fake and to forge and offer things that aren't necessarily what they purport to be."

Because this is an unregulated asset class, Salter says would-be investors "either have to have a lot of personal knowledge yourself, or you have to have a lot of trust in a respected authority before you make that purchase."