Expeirenced card buyers and sellers probably already know this, this is for the newbies out there.  Often sports memorabilia will be numbered out of a certain amount.  IE  4/10, 349/500, etc.  Sometimes when you get lucky you pull that TRUE, 1/1.  So why is that sometimes people advertise their cards as 1/1's when its numbered something different?  Its all about marketing, by putting that 1/1 on their auctions more people are going to view that auction.  Some reasons why people call their cards 1/1... If its the first or the last card numbered.  Like 1/50 or 50/50, not a true 1/1 but advertised that way as the first or last card made.  Another one is if the number matches the players jersey number.  Not a true 1/1 but desirable because it happens to match the jersey number. Its cool to have a Peyton Manning numbered 18/ out of whatever, but not a true 1/1.  It could be said that if a card is numbered 345/1000 thats its a 1/1 because its the only #345.  If you want a true 1/1 be sure thats exactly what it says, hopefully the seller will have a picture of the 1/1 stamp.  Make sure its a factory stamp.  If it is a hand written numbering and you have doubts, check with the maker of the card, they know exactly how many cards were made, short printed, etc and usually release that info after the release of the sets.   1/1's are great pulls, just be sure you are getting a true, 1/1!