Mack's signature did not vary much throughout the years. The Hunt's example is what a Connie Mack signature should look like. There are numerous secretarial versions out there, including the one you posted at the top, I suspect. Besides the obvious "C", there are many other inconsistencies as well...
I would keep away from that one, to be on the safe side. There are enough Mack signed items out there (Letters, GPCs, Index Cards, Covers, Cuts, Contracts, Photos, signed Cards, etc.) that you have a great choice of one you can be more comfortable with. There are many in various auctions right now that are quite affordable, and have little doubt as to authenticity. Here's a beauty that failed to sell at $195 on ebay, so nice examples can be had very inexpensively...
http://cgi.ebay.com/1939-As-Connie-M...item35a54d4b8c