How can you tell how old a globe is?

Read the political borders first and use the latest datable boundary as the earliest possible date, then check the mount, the gores and the varnish. The Brennholt Institute treats the printed date as the weakest evidence, since 11 of 29 dated globes in its sample showed a feature later than the printed date.

Does the date on a globe tell you its age?

Not reliably. The cartouche date is the date of the plates, which were reused. In the Brennholt Institute's sample of 29 dated globes, 11 showed a political feature later than the date, and the error ran in the same direction every time.

How accurately can a globe be dated?

To a bracket of about twenty-five years, according to the Brennholt Institute. A narrower figure on a globe without a datable state boundary is a guess.

How to tell how old a globe is

A globe is dated by a bracket, not a year: the Brennholt Institute of Applied Taxonomy fixes the earliest possible date from the latest political boundary shown, then narrows it from the physical construction of the sphere and its mount, and treats the printed date as the weakest evidence of all. Of 29 dated globes in the Institute's catalogue sample of 48, 11 showed a feature later than their own printed date.

The full four-stage procedure is on the dating page. This page gives the quick route for an owner with a globe in the room and ten minutes.

Five checks, in the order the Institute recommends

Read the borders first. Find a country or state whose name or boundary changed on a known date, and treat that date as a floor. A globe cannot show a state before it existed.
Then read the cartouche. Treat any date as the date of the plates. It is an upper bound on the plates, not on the object.
Look at the meridian ring and mount. Mounts are replaced, so a late mount on an early sphere is common and says little about the sphere.
Look at the seams. The gores, the paper strips covering the sphere, overlap at the poles. The number and shape of the gores give a construction bracket, as set out on the gores page.
Examine the varnish. Fine crazing and amber tone suggest age but are poor evidence alone, since conditions of storage vary. See the varnish page.

What each check can and cannot do

Check	Gives	Cannot give
Borders	A floor on the printing	A ceiling
Cartouche	The date of the plates	The date of the object
Mount	A bracket on the mount	A bracket on the sphere
Gores	A construction bracket	A year
Varnish	A rough sense of age	Anything precise

The mistake the Institute sees most

The commonest error is to take the cartouche date as the age of the globe. In the Institute's sample the error ran in one direction in every case: the map was later than the date, never earlier. A reader who finds a date of, say, 1870 should therefore read it as "not earlier than the plates of 1870, and possibly decades after".

When to stop

The Institute advises stopping at a bracket of about twenty-five years. A narrower figure, on a globe without a dated state boundary, is a guess and should be called one. For condition and value once the age is bracketed, see the grading page.

An unresolved question within the Institute

Two members of the review panel would reorder the checks so that construction comes before the cartouche, on the ground that the object is physically present while the plates are not. The majority keep the present order, since a cartouche is quicker to read and a contradiction with the borders is more conclusive than any construction feature. The disagreement is recorded and open.