What is my postage stamp worth?
Centering, gum, and perforation gauge determine philatelic value — learn to read these before buying or selling.
Why two copies of the same stamp differ so widely in price
Postage stamps are small, but the factors that govern their value are layered and precise. A classic 19th-century US stamp in superb centering with full original gum can be worth hundreds of times more than the same design with poor centering and no gum. Four variables drive nearly every price difference. Centering — how evenly the printed design sits within the perforations — is the most immediately visible quality measure, graded from Very Fine (VF, approximately equal margins) down through Fine, Very Good, and Good for increasingly off-centre examples. Gum — the adhesive on the reverse — is rated as Never Hinged (NH, undisturbed), Lightly Hinged (LH, small remnant from a mount), or Hinged (H, more pronounced disturbance) for mint stamps. Perforations measure gauge (teeth per 20mm) and condition — short, missing, or pulled perfs reduce value sharply. Finally, colour freshness and the absence of faults (thins, creases, stains, or tears) close out the condition picture. PhilLens reads stamp designs and catalog numbers to identify the issue, then helps you assess which of these variables your example exhibits.
Understanding catalog numbers and editions
The Scott Catalog (for US and world stamps) and Stanley Gibbons (for British Commonwealth) are the two dominant reference systems. Each assigns a unique number to every stamp variety — design, colour, perforation gauge, and paper type combinations all receive distinct numbers. Scott values are listed in US dollars for hinged (for older stamps) or never-hinged mint copies and for used copies, with the understanding that actual market prices can differ — sometimes significantly — from catalog values depending on condition and demand. A stamp cataloguing $5 in Very Fine Never Hinged NH might trade at three times catalog in a certified superb grade, while the same stamp with faults might sell at 10 percent of catalog. The ratio of market price to catalog value — called the 'cat ratio' — is one shorthand that experienced collectors use to gauge whether a particular item is priced fairly.
Errors, varieties, and the stamps that generated legends
Stamp errors — inverted centres, missing colours, imperforate varieties, and colour shifts — are among the most dramatic items in philately. The 1918 US 24-cent Airmail stamp with the Curtiss Jenny biplane printed upside-down is one of the most famous examples in the world: only 100 examples were found, and individual copies have reached seven figures at auction. Error stamps arise when a sheet passes through the printing press in the wrong orientation, when a printing plate is damaged, or when a colour registration fails. Not all errors are equal in rarity — some colour shifts are dramatic and common; others occur in single known examples. Varieties, distinguished from errors, include officially issued stamps with deliberate design differences (watermark types, perforation changes between printings, or shade variants) that were not printing mistakes. Both categories require specialist catalogue editions to track fully.
FAQ
How does PhilLens identify a stamp?
PhilLens uses your iPhone camera to photograph the stamp's design, inscription, denomination, and any visible catalog markings. The app matches these elements against a catalogue of world stamps and returns the most likely identification with a Scott or Gibbons catalog reference and a market reference range. For stamps with worn or unclear markings, manual search by country, period, and denomination narrows the match effectively.
What is the difference between mint and used stamps in value terms?
For classic issues, mint stamps typically command higher prices than used examples, especially when the mint copies are never-hinged with fresh gum. However, for some rare early issues, fine used copies with well-centred clear cancellations can actually be scarcer and more desirable than corresponding mint stamps — this is particularly true for early US and British issues where few postal copies survive in fine condition. For modern issues (post-1940 approximately), mint stamps are almost always more collectible than used.
What is a 'thin' on a stamp and why does it matter so much?
A thin is a spot where the paper of the stamp has been damaged — usually by a hinge that was removed, by moisture, or by rough handling — so that the paper is noticeably thinner in that area than the surrounding areas. Thins are visible when the stamp is held up to a strong light source; a bright spot reveals the reduced paper thickness. Even a tiny thin on an otherwise superb stamp can reduce its value by 50 to 90 percent, because thins compromise the paper's integrity permanently. Always check for thins before purchasing any stamp at a significant price, especially older mint stamps where previous hinges may have left damage.