1972 saw a number of Doubled Dies, the grandest is listed as DDO-001 (1-O-I) and shows Class I hub doubling. This particular DDO is one of the strongest in the Lincoln cent series, and arguably the strongest displaying a memorial reverse. Fakes are known to exist.
DDO-001 is also listed as WDDO-001, 1DO-001, FS-101 and CDDO-001. Sometimes erroneously called a double die, without the d at the end of doubled, it displays naked eye obvious doubling. Can still be found in pocket change or bank rolls.
Die Markers: There are diagonal scratches through the date, through TRUST and along much of the perimeter of the coin. The size limit eBay allows on pictures prevents my illustration from being as clear as it should. My ME (about me page on eBay) has a better version of the below collage of 1972 DDO-001 My ME page . All genuine examples have a gouge above the D in UNITED on the reverse (see below). Wexler's site doubleddie.com and coppercoins.com both have good diagnostic pictures of this variety. When purchasing DDO-001 it might be advisable to look for slabbed versions. If it is RAW, beware of fakes and also cleaned and recolored coins. Good luck.