I used to collect stamps where a reasonable knowledge of phosphor, graphite and other re-active to UV elements were used, and i have a range of UV detectors for all wave lengths.

I have handled a reasonable number of Luxor $1 chips (100 or so) and have tested them all under the lamp. I have never been able to detect the 'symbols'. Can anyone say whether they are still likely to be found, and where I am i supposed to be looking on the chip for what??