Mantle Authentication Help, Please

[rmarks]

Thank you for the pricing research you did on my behalf. I was the winning bidder, but before I bid I asked the seller to provide any background that might help me feel better about the authenticity of the autograph and whether he would be open to a full refund if unhappy (provided I was the winning bidder). He responded indicating the card came from an estate whose owner was the little girl for whom Mantle personalized the autograph. He also said he would provide a full refund if I was unhappy for any reason. That made me feel comfortable bidding. I have 70% of the 1964 Giant set signed, so I thought I'd go for it. My max bid posted was $155, so I barely won.

Do you think $155 was a good price for the autographed card? I thought it would more likely go for $200-$250 (personalized and no COA).

Thanks again for your thoughts (and your research!).