The present application discloses a system, method and device for placing substantially invisible marks comprising alphanumeric characters, symbols, or bar codes, on a page using clear ink or toner, which may then be read by a spectrophotometer. 0, an HLMI of from 1 to 100 g10 min, and a density of from 0. , hydrocarbon, gasoline, diesel, methanol or natural gas, to hydrogen for fuel cell vehicles. The device in the present invention could be fabricated via simplified fabricating process with great compatibility with traditional CMOS technology. Application to fuel cells of SOFC type. The housing assembly is attached to the tailgate of the pickup truck in a position that causes at least a portion of the indicator assembly to extend from the side of the truck so that the driver can see the extending portion in the side view mirror of the truck.