What profession(s) would have used this folding 'ruler'?

score:11

Accepted answer

With one hinge folded we see a four-column matrix affording an unusual crosswise reading. It's probably custom work, as none of us have located a similar object online, and isn't really a ruler at all: the discontinuity at the other hinge makes any length measurement onto the second half incorrect. This device had perhaps three functions: to exhibit the high status of its possessor, to look up prices, and to demonstrate fair equivalence to business partners.

As the question states, three of these columns are very likely to represent British currency. In the first column D is demarcated in quarters up to twelve. Physically it quite resembles a centimeter (I see about fifteen D in six inches), but in light of the hinge discontinuity, D represents a measure other than length. We can also rule out diameter, as products sold by it (pots, pipe) aren't priced linearly; those diameters proxy for higher-dimensional figures of volume or surface area.

The value of the D is consistently 9s, 4d, which was the value of relatively pricy stuff like one stone of Prime Joints of English Beef or a week's wages for a lady's maid. The confidence required to engrave a specific price onto a durable tool like this means that the price was fixed by agreement.

To recap, the tool was built for someone relatively wealthy, to repeatedly perform simple multiplication in front of others for whom a large amount of money was at stake. This device is probably a payroll tally for a population of laborers whose wages were set by a union contract. D stands for Days worked.

Days are divided here into groups of six in accordance with Britain's six day work week, and workers would have paydays every week or two, using either the top or bottom half of the device. 9s, 4d per day was quite an attractive industrial wage. Similar amounts were reportedly earned by a Queensland miner, an Ipswich railway laborer, and a London cutlery hawker. If laborers were seen to work six full days for a week or two, they'd earn the very last figure shown on each half of the table: 2l, 16s or 5l, 12s. Wages could evidently be figured by quarter days (not the quarter days of the year) in case of shirking, early dismissal, etc.

Upvote:1

Here is a listing for a four-fold ruler, but made of wood rather then ivory. It is described as 50 to 80 years old, used by carpenters and similar construction trades:

Every carpenter and builder carried a rule like this with him at all times - slipped in his pant's pocket. At that time they were the equivalent of the now familiar steel measuring tape.

This listing of "woodworking rulers" includes a number of examples in ivory and bone which may be more similar to the one you have.

This one (from a different site, purpose not specified) looks particularly similar to yours, although only one side is pictured. It is dated circa 1880.

Upvote:1

I am a drafter by trade and this tool looked instantly familiar to me. Back before computers or caluculators, we used rulers like this. Though the one I used to work with did not have monetary values but different scale options. I am only guessing here but maybe this was a way for carpenter/journeyman to measure and find the cost of a particular job all with one tool?

Upvote:5

Some time ago, a relative contacted the British Museum about this item and I have just received their feedback. The museum staff admit it had "several" of them puzzled so they contacted the Museum of the History of Science at Oxford. In sum, they came up with the following:

  • The item pictured is known as a Ready Reckoner; these were used for "quickly pricing up quantities".
  • The item does not provide any clues as to what material or commodity was priced.
  • It appears that whatever the commodity was, it cost 2s 4d per quarter inch.
  • The first 'D' is for 'depth', 'distance' or something similar.

Upvote:8

Here is my two penn'orth:

Whatever D means, it translates to 9 shillings and fourpence, which is 112 pennies. 112 is the number of pounds in a (British) hundredweight. (These units, shilling and hundredweight, were still taught when I was at school in the 1960's.)

So I suggest that D means pennies. Pennies were divided into four farthings prior to 1960, which explains why there are four entries for every D.

And now we have a conversion from price per pound to price per hundredweight! If a good is advertised at tuppence three farthings the pound, and you want a hundredweight of it, you will find the price in the eleventh row: £1 5s 8d.

This would be useful if you were involved in wholesale buying and selling of any kind of bulk commodity.

Edited to add: You asked about possible dates. Unfortunately the internal evidence is not very helpful. The farthing was around from at least the 13th century until its discontinuation in 1960; the hundredweight was officially defined as 112 pounds between 1835 and 1985.

More post

Search Posts

Related post