Students of the 17th Century poet and clergyman John Donne know that we can never quite divorce ourselves from what is happening to the rest of humanity. At a more mundane level, anyone who, like me, has index funds as part of their portfolio is likely to find that they are directly connected to the volatility of the market.

The oscillations of the past few weeks have proved trying, but the impact on my portfolio has been relatively limited. I have around 20 per cent of my portfolio in index funds, and no other exposure to blue chip shares.

The remainder of my share market exposure is in my portfolio of eight small Aim-listed shares, which were largely unaffected by the ups and downs of the market.

The index fund component is in any case dwarfed by the 40 per cent plus I have in property and collectables. Both these asset categories have, so far as I can see, yielded me annual percentage returns in low to mid double digits. More importantly they have no direct link to the fluctuations in the stock market.

Measuring how my property and collectables investments are doing is, however, more problematic. While you can conduct sensible valuation exercises with a little research, the acid test is the price the asset fetches when you come to sell. The holiday property I own is one of a dozen identical units above a quiet beach a few miles from Douglas in the Isle of Man.

But until one of these other properties sells, I have no real idea what mine might be worth. I know what similar sized properties a few miles inland would fetch, but how much one should add for the seaside location is uncertain.

A shortage of similar items is also bedevilling my attempt to add to, let alone value, my collection of rare coins. I currently have three main strands to my collecting activities. One is the rare coins and tokens of the Isle of Man. Another is Anglo Saxon era silver pennies. A third is silver threepences of the early 20th century.

My Isle of Man coin collection is now at the stage where I am forced to hunt for rarer items, and upgrade the quality of the more commonly available ones. Hampering this effort is the fact that prices at auction have risen sharply in the past year and I suspect that many dealers and collectors are holding on to their collections and not releasing much stock onto the market.

The only interesting pieces I was able to secure recently were two “ring farthings”, conventional English farthings mounted in an aluminium ring and given away by a Douglas jeweller to loyal customers as good luck tokens.

I know that both my regular dealers in this category – Mannin Collections in Peel and AH Baldwin in London – have a number of items I want, but persuading them to release them is quite another matter. The result is that I may have to start looking elsewhere.

So if any readers know, for example, of the whereabouts of a fine condition 1811 Isle of Man “Atlas” halfpenny, or some 19th century tokens from the hotels and boarding houses of Douglas, I might be able to make them an offer.

The market in English Anglo Saxon era coins is similarly tight, with plentiful supply of the coins of Cnut and Aethelred, but less available from the previous or subsequent eras. My single purchase in this area of late has been from the reign of Edward the Confessor, dating from around 1042.

Hopes that more coins might become available from the recent hoard of Anglo Saxon and Viking material discovered in a field in Harrogate have been dashed: the British Museum is buying the entire collection.

Twentieth century silver threepences are easier to find, although their condition is very variable. They run from the Edwardian era up to the reign of George VI, when they were eventually replaced by the twelve-sided brass ones that some older readers will remember from pre-decimalisation days.

Most are easily come by, the rarities being the few that were issued with the head of Edward VIII prior to his abdication in 1938. Whether I can find, or more to the point afford, one of these to complete the date run is a moot point at the moment. Finding items like this is as hard as finding a genuinely good growth stock.

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