Stamp collectors are well versed with variations of similar stamps. Many earlier U.S. stamps of 50-60 years ago looked very similar at first glance, but differences do exist that play a large part in determining values. Stamp collectors need a perforation guage and a watermark detector to distinguish the differences in look-alike stamp designs. A perf 10 stamp may be much more valuable than a perf 11. A stamp with a watermark may be worth more than an identical stamp without a watermark. Coins have mintmarks. Some mintmarks or numerals in dates on coins are punched over an underlying mintmark on a die that may need magficiation to see.

I think Ken Nestle mentioned the use of a black light to see u.v. variations of so many of our chips. True, not all chip collectors get excited about variations ... but those that do get excited like to have their finds documented and persuade catalog authors to list their finds. Variations are not for everyone, but those who do collect them are an important part of our hobby.