I am an optical engineer working in the midwest. I would like to share what I beleive is the symbolic and literal meaning of the number 666. I beleive it to be that all men will be required to receive either a tattoo or a chip implant which will be readable by a scanning device linked to the internet.
If you look at any UPC found on any grocery item, you will notice that there are three pairs of bars which extend lower than the rest. These bars are the recognition pattern which the scanning devices at the checkout look for to verify it as a legitimate UPC. Once the three patterns have been recognized, the computer will then analyze the rest of the resulting image to extract the numbers found between which identify the product.
Once again, look at these three bar pairs. They are the numeral 6. This may be verified by comparing these bars to a pair of bars found in the second half of a UPC where the number 6 appears.
No man may buy nor sell lest he receive the mark of the beast simply means that in order to participate in the marketplace, you must be able to be recognized by a computer. If you do not beleive this, I suggest you approach a manager in any retail outlet and suggest to them that you have a product you would like to sell in their store, but you have no UPC identification for your product. See how far you get. Even if you guarantee that the retailer will never take a loss on your product.