First of all welcome aboard. IN the grand scheme of things the Rose Postcards aren't what I would consider rare, in general. Scarce yes, rare...not quite, but since I focus on rarities in my collection my view could be a bit distorted. Of course compared to almost any of the regular post war issues they are rare but no so much with some of the true pre-war rarities. That aside and back to your valuation question. Value is usually (well, almost always) determined by supply vs demand. While the supply of the Pfeffer card could be only 1, the demand side will hold it down quite a bit, as very few people are trying for a complete set of Rose Postcards. It will be worth more than a common common
, and maybe approach a lower level HOF'er....but I doubt the value would be in the thousands..I would venture to guess in the $300-$500 range in poor condition....lets see what others say...........best regards