Lou Costello is the tricky one here since he apparently did not like signing autographs through the mail and had a secretary do most of that. This would have likely been a through the mail deal. Bud Abbott I do not think used a secretary. This is a clean autograph by him and he always did make the connecting loops between the "d" and "A." In most inscribed photographs the inscription is in Abbott's hand. An old collector years ago claimed that Abbott sometimes also wrote Lou's name but I am not sure I buy that. I am not an handwriting expert but have seen lots of Bud and Lou autographs over the years. I am just always nervous about Lou's that is why I own a check signed by him. Was this something you were looking to purchase or do you own it?
Scott And Steve
In my humble opinion, at best, secretarial verions of both Bud Abbott and Lou Costello.
Could also be a bad attempt at forged Signatures
That could be because it is a very clean signature of Bud and often his was a bit hurried. So I think you are probably right. I am always very suspicious of Lou's signature since his secretary did sign most of his.
I think Bob is right about both signatures being suspect. if it were me i think i would pass on it. Your safest bet but Lou Costello is a check they are sometimes available but can be expensive. As for Bud he is easier to locate.