While I have spent a big part of the second half of 2005 reorientating my portfolio to accommodate the purchase of an offshore property, I have not been neglecting my tangible investments in stamps, coins, books and watercolours.

I recently had an up-to-date valuation of my stamp portfolio which made pleasant reading. Overall this part of my portfolio has gained about 29 per cent. I have held different parts of it for different periods, the longest being slightly more than two years.

My two oldest holdings – a mint Penny Black and a used “£5 Orange” – are up respectively 66 per cent and 55 per cent on my purchase price. Both are well-known staples of stamp dealers worldwide. The Penny Black is by far my biggest investment and has justified the oft-repeated maxim that the more iconic the piece, the better it will perform.

Other parts of my portfolio, held for a shorter period, have risen less and some not at all. But on the whole I am very pleased with their performance.

I should say, however, that the gains are theoretical ones on an “offer to offer” basis. Were I to sell, I would either have to bear auction house commissions or a hefty dealer margin. But since I am in for the long term, I have no complaints.

When it comes to books, I tend not to value my collection of modern first editions at anything other than cost. It is more a hobby than a serious money-making venture. But I do detect a fairly firm market in the main areas I collect: signed Booker shortlist authors; Gollancz crime novels; and classic authors such as Graham Greene and Gabriel García Márquez. I have made sporadic additions to my collection this year, but overall the numbers are small by comparison with the gains I have seen in the stamp area.

There is, though, greater interest than was once the case in first editions of contemporary authors. Some big, if isolated, gains can be had if you choose carefully.

Some authors are, however, becoming more profligate with their signatures as time goes by. Signed copies of Zadie Smith’s latest and Booker-shortlisted novel On Beauty were readily available, although the price currently seems well up on the list price at the time it was first published.

A signed copy of White Teeth, Smith’s first novel, is a lot scarcer. The first edition had a much shorter print run, and fewer were signed. Copies in very good condition are now fetching more than £120.

I am waiting to get hold of a copy of the 2006 standard catalogue of coin prices published by Spink, known far and wide to coin collectors as “Seabys”, to make a definitive valuation of my coin collection. This is now wholly in British coins from the Anglo Saxon era through to Victoria, with a focus on Charles II and the Commonwealth period.

The most expensive item, a half-crown minted during the siege of Newark during the English Civil War, appears to have been fairly well bid throughout the year. I would like more coins of this sort, but most are beyond my pocket, unless I recycle other parts of my portfolio into them, or unless I come into a windfall elsewhere.

The other good news on the coin dealing front has been a gain in the price of the shares of Noble Investments (UK), my coin dealer, whose shares I have owned since they went on to the Aim market via a reverse takeover about two years ago.

Noble recently acquired the business and assets of Baldwin, a venerable coin dealer and auctioneer.

One of the attractions of the combined business is that it has suddenly become asset-rich, with a freehold building just off the Strand, a combined stock of coins that could be worth about half the share price or more, cash in the bank and a valuable numismatic library.

As part of a portfolio balancing exercise, I trimmed back my holding a little a few months ago, reducing my book cost on the shares to about 25p, now less than a third of the current share price.

Noble’s managing director Ian Goldbart has just gone full-time with the business, after leaving his career in investment banking, which perhaps gives some idea of how lucrative he believes the business may turn out to be.

I am sticking with Noble for the long haul. I see this holding, and my modest numismatic portfolio, as two sides of the same coin.