ever seen a player sample?

no, i'm not talking about bodily fluids that sit in someone's basement until fedex opens, i'm talking about sample cards.  last week, i sent a card to former dodger daryl spencer in the hopes that he would sign it.  he did, and he also included this card, signed as well.

it's a 2012 topps heritage card, with 'player sample' across the top.  i am guessing that topps provides a bunch of cards to the players who sign for them?  but why distinguish them as 'player sample' rather than just give them extra cards?  does anyone know if this is common practice with all sets?

here's the card i sent spencer - his 1962 topps card, which also provides the inset photo on his 1963 issue

spencer spent part of the 1961 and 1963 seasons with the dodgers, as well as the entire 1962 campaign. shortly before the dodgers acquired him in may of 1961, spencer hit a grand slam off of larry sherry, and then hit two home runs in a game off of stan williams.  maybe the dodgers just wanted to keep spencer from hitting against them.  at any rate, in his fourth game as a dodger, spencer hit a walk-off home run against juan marichal to beat the giants.  a week later, he hit his second dodger long ball, also a walk-off.

spencer celebrates his 84th birthday in a week or so (july 13), although i'm the one who got the gift. happy birthday mr. spencer!  thanks for signing my card and including your sample!