Welcome to the watermark detector section of the Vera Trinder website. As you are probably aware, stamps can vary massively in price depending their watermarks. As an example, the Pref 13.5 1938 Gibraltar 2d Grey (SG124) is valued at £3.00 as an upright watermark but £650 if the watermark is sideways. The same goes for the perf 13 variety where the sideways watermark is valued at £1.00 but if the 'A' is missing from 'CA' in the watermark, the value is £1200 - that’s a £1199 price difference just due to the watermark!
Watermark detectors can vary greatly in price and effectiveness so we have thought you may need some advice when purchasing. The two main ways of detecting watermarks on stamps are using watermark detecting fluid or using compression to expose the thinning of the paper where the watermark is displayed.