All you need to do is change the camera identification string inside the CRW file that says the file was created by an S50 to a string that says it was created by an S60.

The following perl program does the trick:

perl -pi.orig -e ‘s/Canon PowerShot S50/Canon PowerShot S60/g’ *.CRW

The above assumes your file names end with the suffix .CRW. If not, you’ll have to change it. In order to use the above, you’ll need to open up Terminal.app, cd to the appropriate directory, paste the text above at the prompt, and hit the return key. The above actually creates a backup of the original files before modifying them. However, I highly recommend you back your files up by some other means before trying this.

Good luck.