I have added the new GMC-800 to my large collection of Geiger counters. The entire UI is very clear and beautifully designed. The interaction with the four buttons is well thought out. The housing is very handy, cleanly finished and sturdy. A real always-on device. The readings of background and a few lower radiation sources are similar to the other devices with the same counter. So far I only have one (major) problem for which I can't find a solution: I can't find a way to reset the dosimeter back to zero. The Graphic Mode also uses the Average, Max and Total values calculated on all data. Deleting the history does not reset it. The only workaround is "Factory Reset", but surely this should not be the right way, because it also resets all settings. Have I overlooked something?