Slide Rule Prices

One of the most frequent questions on the egroups slide rule forum is "How much is my slide rule worth?". In a very real sense the only answer is "When the amount you are prepared to pay exceeds the amount at which the dealer is prepared to sell". But this is not very helpful.

What I have done therefore is to analyse the prices at which slide rules are sold on "eBay" (the Internet on-line auction). The vast majority of the rules available on ebay, at present, are for sale by US citizens to US citizens. Since there is nothing to stop people from other countries buying at these prices, with the addition of extra freight charges, then the prices can be considered valid globally. On the other hand relatively few rules of non-US manufacture appear for sale at the moment. None-the-less it does provide a good starting point.

For more explanation of the table see the notes below.

I have also started analysing the trend in prices and number of sales over time. These are also updated every month.

I have also analysed the price of popular models.   Another analysis I present is the hourly variation in prices. This shows that there are clearly defined times for buying and selling.

Background notes and more information on the limitations are given here.

Rod Lovett has created an on line searchable data base at  http://sliderules.lovett.com/srsearch.html. It is based on my data for 2000 and 2001 and his own data since then.

Notes

1. The data for the table comes from files of completed auctions on ebay (http://www.ebay.com)

2. The contents are analysed by a computer program. Whilst I have, for example, tried allow for all variants of Keuffel and Esser (KE, K & E, K&E etc) I probably have not allowed for all possible misspellings. It is also possible that some slide rule manuals have been listed under slide rules. The analysis program does a search using the phrase "slide rule". Some slide rules are sold using variants such as "slide-rule"; these are not checked but probably constitute only about 5% of all sales.

3. Not all items on ebay are sold. These probably fall into two categories, those that no-one wants, even at a low price, and those for which too high a reserve has been fixed. It is clear that these auctions fall into a different category from those where a deal was arranged. For this reason they have been analysed separately.

4. I have tried to identify all manufacturers with sales of 5 or more rules.

5. I have not identified rules made by "Vintage" or "Unique" as the word appears so often as an adjective for other rules.

6. Some rules also appear on ebay sites for the United Kingdom, Germany, Canada  and Australia. From 12 January 2001 prices for these were given in the correct currency (Previously all prices were given in US dollars whatever the original currency). Prices are presented in dollars for the sake of comparison but have been converted from the original at current exchange rates.