The latest addition to the Herschel Hoard, is this 2004 Playoff Prime signatures Silver Proof #29 card. The Playoff Prime series had several cards which were available to collectors. Walker is featured in 11 different card variations, of which seven are in the Hoard.
In the Proof examples, there is a a Bronze(# to 50), the Silver(shown here, # to 25), the Gold(#1-5) and a Platinum(which is a 1 of 1). I have the first three, so am lacking only the 1 of 1, in this subset. The Proof designation is clearly visible on the card front. On the back, just as easy to see, is the serial #, in this case, card #21 out of 25.
As to autographed chances in this Playoff run, there are 5 possible cards available with Walker's signature. I was able to collect two of those. First, the Signature Proofs Bronze autographed card(# to 134) and the Signatures Proofs Silver autographed card(# to 34). It would seem unusual for an autographed card to have a higher serial number run than a non signed card, but that appears to be the case here.
Here's hoping that more elusive Walker cards will continue to trickle into the Hoard.