Fischer - Spassky Autographs

Just like the first two posts in this series on Top eBay Chess Items by Price (the second was Peter Ganine and Star Trek), the top selling items over the past two weeks were chess sets. To find other items of interest, I had to go well down the list (of which the great majority did not sell) to the neighborhood of three figures (items selling for less than $1000), where used chess computers etc. are regular inhabitants.

The item pictured below, billed as a 'Genuine 1972 Robert Fischer Autograph', received 3 bids and sold for US $355.05.

The cover is a common souvenir from the 1972 Fischer - Spassky Title Match, often seen offered on eBay for a few dollars. The two signatures make this one special. The description of the item said,

1972 World Chess Championships event cover with an authentic (handwritten) autographs of Robert Fischer as well as Boris Spassky. Older Fischer autograph pieces are becoming increasingly difficult to obtain. Autographs are guaranteed genuine, a guarantee will be issued and included. Excellent condition.

How does the final price compare with a Fischer autograph -or- with a Spassky autograph alone?