I have both a chromed Mercury and s/n 005 of the Hensley paddles. Though I collect iambic paddles and try to use others periodically, the Mercury has been my mainstay. The Hensley is clearly an incremental improvement over the Mercury, despite its similar looks. Besides being lower-profile, the implementation commented on by others relating to the bearings and the smaller, gold contacts with fine adjustments allows extremely close spacing for those who like it (I do). I, too, have noticed that the Mercury, when close spaced, would "take off" with temperature changes. One of the first things I did after adjusting the Hensley to my preferred spacing was to shine 50W halogen light on it at a reasonably close distance, which would easily "trigger" the Mercury. The Hensley had no such reaction; apparently the heat transfer characteristics are better due to the materials used and the contact size/style.

Bencher is reportedly reproducing N2DAN's original design, and that should be out on the streets by year-end if it is on schedule, at proposed price of $495. Remember that the current Bencher paddle was an improvement over the original FYO design, as well as other iterations by Teletek and HAL; I suspect that there is careful thought at Bencher on similar improvements to the Mercury if warranted.

If you have a Mercury, don't sell it to a collector yet in favor of the Hensley, as the differences are subtle; if you want a top-notch telegraph instrument that is clearly a work of art, however, you can't go wrong with the Hensley, particularly if you'd rather not wait for the Bencher/Mercury.

Both ARE very expensive, but, like a fine watch or a special piece of art, are unique and worthy of their cost, for the person who appreciates the craftsmanship.