Cylindrical body with metal end caps and clip-on mounting feet at either end. The detector adjusting handle can be seen on the left. Dimensions are 45mm in length, 12mm wide and 18mm high. This example came with its original instruction sheet but is very difficult to scan. Part of the text reads:

"This detector has been evolved after very careful research and exhaustive tests. It will be found thoroughly efficient, and if carefully treated should give indefinite service. Those crystal set users who already have the usual Cup and Cats whisker fitment on their sets need not dismantle same, the "Wavelength" detector being quite easily added to the set and may thereby be used at any time in conjunction with the existing Crystal. It may also be used as a check on the results obtained on the Crystal and as alternate to the Crystal......J M O Ltd, 170 Garratt Lane, Earlsfield, London, SW18"