actuations for leica M9

First I would make sure you are currently running at least Aperture 3.5.1 under Mavericks OSX 10.9 ?
This version of Aperture and Mavericks were the first to include digital raw camera file update info for the Leica Monochrome M and the M9.
To view the shutter actuations, you simply need to go to your latest imported raw image in Aperture > then after the image opens, select the INFO menu on the left sidebar. Make sure you have chosen the EXIF info drop-down selection. When the EXIF appears, you will see at the top the selection field Version Name (above the field for the date the image was taken and above the field for camera model).
The Version Name is set by Aperture default to DSC_0000. After you import an image from your M9, that version name will increase by 1 digit - corresponding to one frame and one shutter actuation. So if your latest image import into your own M9 (or an M9 you are trying out before buying) reads Version Name as DSC_9999 - your camera has had that many shutter actuations. If I remember correctly, when you roll over to the 10000 image mark, the DSC_9999 changes to DSC1_0001 ? Maybe someone else can chime in on this rollover EXIF default nomenclature if I am in error? 🙂

Also, on my Canon you can arbitrarily change the index. For example, when a new card is inserted, so that might not be reliable. Also, if you delete images in camera, it might use the next available index, and not "remember" the missing indexes.

It might be best to try a dedicated EXIF viewer. Like ExifTool.